feat: add git worktree session support with improved UI

Implement comprehensive worktree session support allowing users to spawn sessions in temporary git worktrees. Includes backend worktree management, full-stack integration, and refined UI for session type selection.

Backend:
- Add worktree creation/removal utilities with branch management
- Track worktree metadata (basePath, branch, name, path) in session metadata
- Automatic cleanup of worktrees when sessions fail or exit
- Enhanced error handling with stderr tail logging

UI improvements:
- Redesign session type toggle with improved alignment and spacing
- Move worktree description inline with label for cleaner layout
- Add branch name input field that appears when worktree mode selected
- Auto-focus on worktree input when switching modes
- Reduce gap between radio options from gap-3 to gap-1.5
- Update descriptive text and placeholders for clarity

Integration:
- Thread worktree parameters through API client, RPC handlers, and daemon
- Add worktreeEnv utility to read worktree info from environment
- Update session spawning to support both simple and worktree modes

cli/src/codex/runCodex.ts

@@ -18,6 +18,7 @@ import packageJson from '../../package.json';
 import { runtimePath } from '@/projectPath';
 import type { CodexSession } from './session';
 import { parseCodexCliOverrides } from './utils/codexCliOverrides';
+import { readWorktreeEnv } from '@/utils/worktreeEnv';
 
 export { emitReadyIfIdle } from './utils/emitReadyIfIdle';
 
@@ -50,6 +51,7 @@ export async function runCodex(opts: {
         controlledByUser: false
     };
 
+    const worktreeInfo = readWorktreeEnv();
     const metadata: Metadata = {
         path: workingDirectory,
         host: os.hostname(),
@@ -65,7 +67,8 @@ export async function runCodex(opts: {
         startedBy,
         lifecycleState: 'running',
         lifecycleStateSince: Date.now(),
-        flavor: 'codex'
+        flavor: 'codex',
+        worktree: worktreeInfo ?? undefined
     };
 
     const response = await api.getOrCreateSession({ tag: sessionTag, metadata, state });