refactor: Enhance session management and error handling in AgentService and related components

- Improved session handling by implementing ensureSession to load sessions from disk if not in memory, reducing "session not found" errors.
- Enhanced error messages for non-existent sessions, providing clearer diagnostics.
- Updated CodexProvider and OpencodeProvider to improve error handling and messaging.
- Refactored various routes to use async/await for better readability and error handling.
- Added event emission for merge and stash operations in the MergeService and StashService.
- Cleaned up error messages in AgentExecutor to remove redundant prefixes and ANSI codes for better clarity.

apps/server/src/routes/worktree/index.ts

@@ -80,7 +80,7 @@ export function createWorktreeRoutes(
     '/merge',
     validatePathParams('projectPath'),
     requireValidProject,
-    createMergeHandler()
+    createMergeHandler(events)
   );
   router.post(
     '/create',
@@ -126,7 +126,12 @@ export function createWorktreeRoutes(
     requireValidWorktree,
     createListBranchesHandler()
   );
-  router.post('/switch-branch', requireValidWorktree, createSwitchBranchHandler(events));
+  router.post(
+    '/switch-branch',
+    validatePathParams('worktreePath'),
+    requireValidWorktree,
+    createSwitchBranchHandler(events)
+  );
   router.post('/open-in-editor', validatePathParams('worktreePath'), createOpenInEditorHandler());
   router.post(
     '/open-in-terminal',
@@ -230,7 +235,7 @@ export function createWorktreeRoutes(
     '/stash-apply',
     validatePathParams('worktreePath'),
     requireGitRepoOnly,
-    createStashApplyHandler()
+    createStashApplyHandler(events)
   );
   router.post(
     '/stash-drop',