fix(cliproxy): register session on dashboard start and add port-based stop fallback

Dashboard Stop/Update buttons failed with contradictory errors:
- Stop: "No active CLIProxy session found"
- Update: "CLIProxy was already running"

Root cause: service-manager spawned proxy but never called registerSession(),
so stopProxy() couldn't find the lock file.

Changes:
- service-manager.ts: Add registerSession() after spawn
- session-tracker.ts: Make stopProxy() async with port-based fallback
- routes.ts: Update proxy-stop endpoint to async
- cliproxy-command.ts: Update handleStop() to await async stopProxy()
- port-utils.ts: Fix double-escaped regex for Windows port detection
- session-tracker.test.js: Update tests for async stopProxy()

tests/unit/cliproxy/session-tracker.test.js

@@ -299,13 +299,13 @@ describe('Session Tracker', function () {
   });
 
   describe('stopProxy', function () {
-    it('should return error when no lock exists', function () {
-      const result = stopProxy();
+    it('should return error when no lock exists', async function () {
+      const result = await stopProxy();
       assert.strictEqual(result.stopped, false);
       assert.strictEqual(result.error, 'No active CLIProxy session found');
     });
 
-    it('should cleanup stale lock when proxy is not running', function () {
+    it('should cleanup stale lock when proxy is not running', async function () {
       // Create lock with dead PID
       const lock = {
         port: testPort,
@@ -315,7 +315,7 @@ describe('Session Tracker', function () {
       };
       fs.writeFileSync(sessionLockPath, JSON.stringify(lock));
 
-      const result = stopProxy();
+      const result = await stopProxy();
       assert.strictEqual(result.stopped, false);
       assert.ok(result.error.includes('not running'));
       assert.strictEqual(fs.existsSync(sessionLockPath), false);