Fix PATH resolution aborting on first non-NotFound stat error

The resolution loops in resolveCommandPathForPlatform used
Effect.mapError on isExecutableFile, which propagated PlatformErrors
(e.g. PermissionDenied) and short-circuited the generator on the first
failing probe. This prevented subsequent PATH entries from being
checked.

Extract a probeExecutable helper that uses Effect.catch to convert
probe errors into false, allowing the loop to continue scanning all
PATH entries and command candidates. The last encountered probe error
is preserved and attached as the cause on the final
CommandResolutionError when no executable is found.

Author: cursoragent

packages/shared/src/shell.ts

@@ -552,17 +552,22 @@ const resolveCommandPathForPlatform = Effect.fn("shell.resolveCommandPathForPlat
     path.extname,
   );
 
+  let lastProbeCause: PlatformError.PlatformError | undefined;
+  const probeExecutable = (filePath: string) =>
+    isExecutableFile(filePath, platform, windowsPathExtensions).pipe(
+      Effect.catch((error) => {
+        lastProbeCause = error;
+        return Effect.succeed(false as const);
+      }),
+    );
+
   if (command.includes("/") || command.includes("\\")) {
     for (const candidate of commandCandidates) {
-      if (
-        yield* isExecutableFile(candidate, platform, windowsPathExtensions).pipe(
-          Effect.mapError((cause) => new CommandResolutionError({ command, platform, cause })),
-        )
-      ) {
+      if (yield* probeExecutable(candidate)) {
         return candidate;
       }
     }
-    return yield* new CommandResolutionError({ command, platform });
+    return yield* new CommandResolutionError({ command, platform, cause: lastProbeCause });
   }
 
   const pathValue = resolvePathEnvironmentVariable(env);
@@ -580,16 +585,12 @@ const resolveCommandPathForPlatform = Effect.fn("shell.resolveCommandPathForPlat
   for (const pathEntry of pathEntries) {
     for (const candidate of commandCandidates) {
       const candidatePath = path.join(pathEntry, candidate);
-      if (
-        yield* isExecutableFile(candidatePath, platform, windowsPathExtensions).pipe(
-          Effect.mapError((cause) => new CommandResolutionError({ command, platform, cause })),
-        )
-      ) {
+      if (yield* probeExecutable(candidatePath)) {
         return candidatePath;
       }
     }
   }
-  return yield* new CommandResolutionError({ command, platform });
+  return yield* new CommandResolutionError({ command, platform, cause: lastProbeCause });
 });
 
 export const resolveCommandPath = Effect.fn("shell.resolveCommandPath")(function* (