feat(tui): add web server auto-start, shell mode, and feature parity

TUI now checks if web server is running on startup and offers to start
it in the background. Added new CLI options: --with-web (auto-start),
--no-web (skip check), -p (port).

TUI feature parity with web interface:
- Shell mode: press 'h' in cases view to start bash instead of Claude
- Multi-start: press 'm' to start 1-20 sessions at once
- Respawn toggle: Ctrl+R to enable/disable respawn on Claude sessions
- Session rename: API support via useSessionManager hook

Security fixes from previous analysis:
- Command injection prevention in screen-manager.ts
- Path traversal protection in server.ts
- Input validation for shell-interpolated values

Also fixes memory leak in session.ts (timer tracking) and flaky test
timeout in session-cleanup.test.ts.

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

src/types.ts

@@ -299,6 +299,8 @@ export interface CreateCaseRequest {
 export interface QuickStartRequest {
   /** Optional case name, defaults to 'testcase' */
   caseName?: string;
+  /** Session mode: 'claude' for Claude CLI, 'shell' for bash shell */
+  mode?: 'claude' | 'shell';
 }
 
 /**