fix(server): walk into Cause Fail reasons when detecting nested interrupt causes

findInterruptCause previously returned undefined immediately upon
encountering any Cause that was not interrupt-only, without inspecting
the Fail reasons' error values. This meant a Cause like
Cause.fail(new Error('cancelled', { cause: Cause.interrupt() }))
would not be recognized as an interrupt, causing failEnvironmentInternal
to log a synthetic 500 error and fail with EnvironmentHttpInternalError
instead of re-propagating the interruption.

Extract the loop body into a recursive walkForInterrupt helper that,
upon hitting a non-interrupt-only Cause, iterates Fail reasons and
continues walking each error's .cause chain. The depth budget and
seen-set are shared across recursive calls to prevent unbounded
traversal.

Author: cursoragent

apps/server/src/auth/http.ts

@@ -83,10 +83,27 @@ function failureLogAttributes(input: unknown) {
 
 function findInterruptCause(input: unknown): Cause.Cause<never> | undefined {
   const seen = new Set<object>();
+  return walkForInterrupt(input, seen, 0);
+}
+
+function walkForInterrupt(
+  input: unknown,
+  seen: Set<object>,
+  depth: number,
+): Cause.Cause<never> | undefined {
   let current = input;
-  for (let depth = 0; depth < MAX_CAUSE_CHAIN_DEPTH; depth += 1) {
+  for (let d = depth; d < MAX_CAUSE_CHAIN_DEPTH; d += 1) {
     if (Cause.isCause(current)) {
-      return Cause.hasInterruptsOnly(current) ? (current as Cause.Cause<never>) : undefined;
+      if (Cause.hasInterruptsOnly(current)) {
+        return current as Cause.Cause<never>;
+      }
+      for (const reason of current.reasons) {
+        if (Cause.isFailReason(reason)) {
+          const found = walkForInterrupt(reason.error, seen, d + 1);
+          if (found !== undefined) return found;
+        }
+      }
+      return undefined;
     }
     if (typeof current !== "object" || current === null || seen.has(current)) {
       return undefined;