refactor: migrate Js.String2 to String across src/ (107 occurrences)

Replace deprecated Js.String2 API with modern String equivalents:
- startsWith, length, includes, toLowerCase, toUpperCase

Part of #28.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: hyperpolymath

src/app/devices/CoprocessorBridge.res

@@ -139,9 +139,9 @@ let formatResult = (domain: string, cmd: string, result: executionResult): strin
 // Returns a synchronous dispatch-confirmation string.  The async result is
 // appended to the device's output buffer via Promise.then and collected by RECV.
 let handleSend = (deviceId: string, spec: string, dataArgs: array<string>): string => {
-  if Js.String2.length(deviceId) == 0 {
+  if String.length(deviceId) == 0 {
     "send: no device attached — open a terminal on a hacked device first"
-  } else if Js.String2.length(spec) == 0 {
+  } else if String.length(spec) == 0 {
     "send: usage: send <domain>:<cmd> [int ...]\n" ++
     "  domains: crypto  io  maths  vector  neural  physics  quantum  audio  tensor  graphics"
   } else {
@@ -153,7 +153,7 @@ let handleSend = (deviceId: string, spec: string, dataArgs: array<string>): stri
     } else {
       let domainStr = String.slice(spec, ~start=0, ~end=colonIdx)
       let cmdStr    = String.sliceToEnd(spec, ~start=colonIdx + 1)
-      if Js.String2.length(cmdStr) == 0 {
+      if String.length(cmdStr) == 0 {
         `send: missing command after ":" in "${spec}" — e.g. "crypto:hash"`
       } else {
         switch parseDomain(domainStr) {
@@ -210,7 +210,7 @@ let handleSend = (deviceId: string, spec: string, dataArgs: array<string>): stri
 // as a single string separated by horizontal rules.  Clears the buffer
 // atomically after reading.  Returns a notice if no results are pending.
 let handleRecv = (deviceId: string): string => {
-  if Js.String2.length(deviceId) == 0 {
+  if String.length(deviceId) == 0 {
     "recv: no device attached"
   } else {
     let buf = getBuffer(deviceId)
@@ -235,7 +235,7 @@ let handleRecv = (deviceId: string): string => {
 // Delegates to Kernel.getDeviceReport, which reports compute / memory /
 // energy utilisation with percentages and raw values.
 let getDeviceStatus = (deviceId: string): string => {
-  if Js.String2.length(deviceId) == 0 {
+  if String.length(deviceId) == 0 {
     "coproc: no device attached"
   } else {
     Kernel.getDeviceReport(deviceId)

src/app/devices/DeviceView.res

@@ -189,7 +189,7 @@ let createFile = (deviceIp: string, path: string, name: string, content: string)
       | None =>
         let contentId = GlobalNetworkData.storeContent(
           ~content,
-          ~sizeMB=Float.fromInt(Js.String2.length(content)) /. 1024.0 /. 1024.0,
+          ~sizeMB=Float.fromInt(String.length(content)) /. 1024.0 /. 1024.0,
         )
         Dict.set(
           contents,

src/app/devices/FirewallDevice.res

@@ -123,13 +123,13 @@ let checkPacket = (
     // Simplified subnet matching  check prefix
     let sourceMatch =
       rule.sourceSubnet == "0.0.0.0/0" ||
-        Js.String2.startsWith(
+        String.startsWith(
           source,
           String.slice(rule.sourceSubnet, ~start=0, ~end=String.indexOf(rule.sourceSubnet, "/")),
         )
     let destMatch =
       rule.destSubnet == "0.0.0.0/0" ||
-        Js.String2.startsWith(
+        String.startsWith(
           dest,
           String.slice(rule.destSubnet, ~start=0, ~end=String.indexOf(rule.destSubnet, "/")),
         )

src/app/devices/GlobalNetworkData.res

@@ -62,7 +62,7 @@ let updateContent = (~oldId: string, ~newContent: string): string => {
   // Get size from old content
   let sizeMB = switch Dict.get(contentStore, oldId) {
   | Some(old) => old.sizeMB
-  | None => Belt.Int.toFloat(Js.String2.length(newContent)) /. 1024.0 /. 1024.0
+  | None => Belt.Int.toFloat(String.length(newContent)) /. 1024.0 /. 1024.0
   }
 
   // Store new content (may reuse if hash matches existing)

src/app/devices/NetworkZones.res

@@ -230,14 +230,14 @@ let allZones: array<networkZone> = [
 // Get zone by IP address
 let getZoneByIp = (ip: string): option<networkZone> => {
   // Special handling for multi-subnet zones
-  if Js.String2.startsWith(ip, "142.250.") {
+  if String.startsWith(ip, "142.250.") {
     Belt.Array.getBy(allZones, zone => zone.id == "service-atlas")
-  } else if Js.String2.startsWith(ip, "104.16.") {
+  } else if String.startsWith(ip, "104.16.") {
     Belt.Array.getBy(allZones, zone => zone.id == "service-nexus")
   } else {
     // Standard subnet matching
     Belt.Array.getBy(allZones, zone => {
-      zone.subnet != "" && Js.String2.startsWith(ip, zone.subnet)
+      zone.subnet != "" && String.startsWith(ip, zone.subnet)
     })
   }
 }

src/app/devices/Terminal.res

@@ -81,7 +81,7 @@ let updateInputLine = (terminal: t): unit => {
 let listDirectory = (terminal: t, path: string, activeIp: string): string => {
   switch Some(activeIp) {
   | Some(ip) =>
-    let fullPath = if Js.String2.startsWith(path, "C:\\") || Js.String2.startsWith(path, "/") {
+    let fullPath = if String.startsWith(path, "C:\\") || String.startsWith(path, "/") {
       path
     } else {
       terminal.currentDirectory ++ "\\" ++ path
@@ -137,7 +137,7 @@ let changeDirectory = (terminal: t, path: string, activeIp: string): string => {
       }
       ""
     } else {
-      let newPath = if Js.String2.startsWith(path, "C:\\") {
+      let newPath = if String.startsWith(path, "C:\\") {
         path
       } else {
         terminal.currentDirectory ++ "\\" ++ path
@@ -159,7 +159,7 @@ let readFile = (terminal: t, fileName: string, activeIp: string): string => {
   switch Some(activeIp) {
   | None => "cat: no device IP configured"
   | Some(ip) =>
-    let fullPath = if Js.String2.startsWith(fileName, "C:\\") {
+    let fullPath = if String.startsWith(fileName, "C:\\") {
       fileName
     } else {
       terminal.currentDirectory ++ "\\" ++ fileName
@@ -299,7 +299,7 @@ let handleBuiltInCommand = (terminal: t, cmd: string, args: array<string>): stri
     let hasForce = Belt.Array.some(args, arg => arg == "-f" || arg == "-rf" || arg == "-fr")
 
     // Get filename (skip flags)
-    let fileName = Belt.Array.getBy(args, arg => !Js.String2.startsWith(arg, "-"))
+    let fileName = Belt.Array.getBy(args, arg => !String.startsWith(arg, "-"))
 
     switch fileName {
     | None => "rm: missing operand"
@@ -334,7 +334,7 @@ let handleBuiltInCommand = (terminal: t, cmd: string, args: array<string>): stri
       switch getActiveState(terminal) {
       | None => "cp: no device state"
       | Some(activeState) =>
-        let sourcePath = if Js.String2.startsWith(sourceName, "C:\\") {
+        let sourcePath = if String.startsWith(sourceName, "C:\\") {
           sourceName
         } else {
           terminal.currentDirectory ++ "\\" ++ sourceName
@@ -782,7 +782,7 @@ Cross-VM: Use SEND to port "net:<ip>:<port>" to deliver data.`
         }
       | "chat" | "say" => {
           let message = Array.sliceToEnd(args, ~start=1)->Array.join(" ")
-          if Js.String2.length(String.trim(message)) > 0 {
+          if String.length(String.trim(message)) > 0 {
             MultiplayerClient.sendChat(MultiplayerGlobal.client, ~message)
             `[you] ${message}`
           } else {
@@ -930,10 +930,10 @@ let handleKeyInput = (terminal: t, key: string): unit => {
     terminal.currentInput = String.slice(
       terminal.currentInput,
       ~start=0,
-      ~end=Js.String2.length(terminal.currentInput) - 1,
+      ~end=String.length(terminal.currentInput) - 1,
     )
     updateInputLine(terminal)
-  } else if Js.String2.length(key) == 1 {
+  } else if String.length(key) == 1 {
     terminal.currentInput = terminal.currentInput ++ key
     updateInputLine(terminal)
   }

src/app/devices/VMBridge.res

@@ -338,7 +338,7 @@ let checkPuzzleSolved = (): option<string> => {
 // Parse a VM command string into an instruction
 let parseVMCommand = (input: string): option<vmInstruction> => {
   let tokens =
-    String.split(String.trim(input), " ")->Belt.Array.keep(t => Js.String2.length(String.trim(t)) > 0)
+    String.split(String.trim(input), " ")->Belt.Array.keep(t => String.length(String.trim(t)) > 0)
   let opcode = tokens[0]->Belt.Option.map(String.toUpperCase)
   switch opcode {
   // Tier 0: Register arithmetic
@@ -508,7 +508,7 @@ let builtinPuzzles: array<puzzleData> = [
 
 // Handle 'vm' command  direct VM instruction execution
 let handleVMCommand = (args: string): string => {
-  if Js.String2.length(String.trim(args)) == 0 {
+  if String.length(String.trim(args)) == 0 {
     `vm  Reversible VM Terminal
 Usage:
   vm <instruction>     Execute a reversible instruction
@@ -592,11 +592,11 @@ TIER 2  Stack & Memory:
 Every instruction is perfectly reversible. Use 'vm undo' to reverse.`
     | _ =>
       // Check for memory display command: MEM <start> <len>
-      if Js.String2.startsWith(upperTrimmed, "MEM") {
+      if String.startsWith(upperTrimmed, "MEM") {
         switch bridge.vm {
         | Some(vm) => {
             let memTokens =
-              String.split(String.trim(trimmed), " ")->Belt.Array.keep(t => Js.String2.length(t) > 0)
+              String.split(String.trim(trimmed), " ")->Belt.Array.keep(t => String.length(t) > 0)
             let start = memTokens[1]->Option.flatMap(x => Int.fromString(x))->Belt.Option.getWithDefault(0)
             let length = memTokens[2]->Option.flatMap(x => Int.fromString(x))->Belt.Option.getWithDefault(16)
             let lines = ref([])
@@ -659,7 +659,7 @@ Every instruction is perfectly reversible. Use 'vm undo' to reverse.`
 // Handle 'puzzle' command  load and start a puzzle
 let handlePuzzleCommand = (name: string): string => {
   let trimmedName = String.trim(String.toLowerCase(name))
-  if Js.String2.length(trimmedName) == 0 {
+  if String.length(trimmedName) == 0 {
     // List puzzles
     let lines = Belt.Array.map(builtinPuzzles, p => {
       `  ${String.toLowerCase(

src/app/enemies/Distraction.res

@@ -133,7 +133,7 @@ let kindToString = (kind: distractionKind): string => {
 }
 
 let kindFromString = (s: string): option<distractionKind> => {
-  switch Js.String2.toLowerCase(s) {
+  switch String.toLowerCase(s) {
   | "pizza" | "pizzadelivery" | "pizza_delivery" => Some(PizzaDelivery)
   | "maintenance" | "maint" => Some(FakeMaintenance)
   | "fire" | "firealarm" | "fire_alarm" => Some(FireAlarm)

src/app/multiplayer/VMMessageBus.res

@@ -106,7 +106,7 @@ let classifyPort = (port: string): messageTarget => {
     CoopChat
   } else if port == "coop:item" {
     CoopItem
-  } else if Js.String2.startsWith(port, "covert:") {
+  } else if String.startsWith(port, "covert:") {
     CovertLinkChannel
   } else {
     DevicePort

src/app/multiplayer/VMNetwork.res

@@ -103,7 +103,7 @@ let getDeviceVMByIp = (ip: string): option<deviceVM> => {
 
 let routePortMessage = (sourceDeviceId: string, port: string, value: int): unit => {
   // Parse net:<ip>:<subport> format
-  if Js.String2.startsWith(port, "net:") {
+  if String.startsWith(port, "net:") {
     let parts = String.split(port, ":")
     let targetIp = parts[1]->Belt.Option.getWithDefault("")
     let _subPort = parts[2]->Belt.Option.getWithDefault("default")
@@ -113,7 +113,7 @@ let routePortMessage = (sourceDeviceId: string, port: string, value: int): unit
     }
     ignore(sourceDeviceId)
   } // Covert link channels: data passes through the covert link
-  else if Js.String2.startsWith(port, "covert:") {
+  else if String.startsWith(port, "covert:") {
     let connId = String.sliceToEnd(port, ~start=7)
     switch CovertLink.Registry.get(connId) {
     | Some(conn) =>