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/tui/components/HelpOverlay.tsx

@@ -27,17 +27,30 @@ interface ShortcutGroup {
 
 const SHORTCUT_GROUPS: ShortcutGroup[] = [
   {
-    title: 'Start Screen',
+    title: 'Start Screen - Sessions',
     shortcuts: [
-      { key: '\u2191/\u2193', description: 'Navigate session list' },
+      { key: '\u2191/\u2193', description: 'Navigate list' },
       { key: 'Enter', description: 'View session in TUI' },
       { key: 'a', description: 'Attach to screen (full terminal)' },
       { key: 'd', description: 'Delete/kill selected session' },
-      { key: 'n', description: 'Create new session' },
-      { key: 'r', description: 'Refresh session list' },
+      { key: 'c', description: 'Switch to cases view' },
+      { key: 'n', description: 'Quick-start new session' },
+      { key: 'r', description: 'Refresh list' },
       { key: 'q', description: 'Quit' },
     ],
   },
+  {
+    title: 'Start Screen - Cases',
+    shortcuts: [
+      { key: '\u2191/\u2193', description: 'Navigate list' },
+      { key: 'Enter', description: 'Start Claude session with case' },
+      { key: 'h', description: 'Start Shell session with case' },
+      { key: 'm', description: 'Multi-start (1-20 sessions)' },
+      { key: 'n', description: 'Create new case' },
+      { key: 's', description: 'Switch to sessions view' },
+      { key: 'r', description: 'Refresh list' },
+    ],
+  },
   {
     title: 'Main View - Navigation',
     shortcuts: [
@@ -53,6 +66,7 @@ const SHORTCUT_GROUPS: ShortcutGroup[] = [
       { key: 'Ctrl+N', description: 'New session' },
       { key: 'Ctrl+W', description: 'Close current session' },
       { key: 'Ctrl+K', description: 'Kill all sessions' },
+      { key: 'Ctrl+R', description: 'Toggle respawn (Claude sessions only)' },
     ],
   },
   {