fix: SDK Agent fails on Windows when username contains spaces (#1022)

* fix: SDK Agent fails on Windows when username contains spaces

Fixes spawn failure on Windows when the user's path contains spaces
(e.g., C:\Users\Anderson Wang\).

Root cause:
- SDKAgent.ts returns full auto-detected path with spaces
- ProcessRegistry.ts cannot execute .cmd files when path contains spaces

Solution:
- SDKAgent: On Windows, prefer "claude.cmd" via PATH instead of full path
- ProcessRegistry: Use cmd.exe /d /c wrapper for .cmd files on Windows

This preserves argument boundaries (e.g., empty string values) while
properly handling paths with spaces.

Fixes #1014

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* docs: add Windows spawn path with spaces fix documentation

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

src/services/worker/ProcessRegistry.ts

@@ -282,13 +282,24 @@ export function createPidCapturingSpawn(sessionDbId: number) {
     env?: NodeJS.ProcessEnv;
     signal?: AbortSignal;
   }) => {
-    const child = spawn(spawnOptions.command, spawnOptions.args, {
-      cwd: spawnOptions.cwd,
-      env: spawnOptions.env,
-      stdio: ['pipe', 'pipe', 'pipe'],
-      signal: spawnOptions.signal, // CRITICAL: Pass signal for AbortController integration
-      windowsHide: true
-    });
+    // On Windows, use cmd.exe wrapper for .cmd files to properly handle paths with spaces
+    const useCmdWrapper = process.platform === 'win32' && spawnOptions.command.endsWith('.cmd');
+
+    const child = useCmdWrapper
+      ? spawn('cmd.exe', ['/d', '/c', spawnOptions.command, ...spawnOptions.args], {
+          cwd: spawnOptions.cwd,
+          env: spawnOptions.env,
+          stdio: ['pipe', 'pipe', 'pipe'],
+          signal: spawnOptions.signal,
+          windowsHide: true
+        })
+      : spawn(spawnOptions.command, spawnOptions.args, {
+          cwd: spawnOptions.cwd,
+          env: spawnOptions.env,
+          stdio: ['pipe', 'pipe', 'pipe'],
+          signal: spawnOptions.signal, // CRITICAL: Pass signal for AbortController integration
+          windowsHide: true
+        });
 
     // Capture stderr for debugging spawn failures
     if (child.stderr) {