feat(tui): add delete session from start screen

- Press 'd' or 'x' to delete/kill selected session
- Auto-adjust selection index when sessions are removed
- Update footer controls with delete shortcut
- Update help overlay with delete shortcut

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

src/tui/App.tsx

@@ -204,6 +204,11 @@ export function App(): React.ReactElement {
     return <HelpOverlay onClose={() => setShowHelp(false)} />;
   }
 
+  // Handle delete session from start screen
+  const handleDeleteSession = useCallback((session: ScreenSession) => {
+    killSession(session.sessionId);
+  }, [killSession]);
+
   // Render start screen
   if (viewMode === 'start') {
     return (
@@ -211,6 +216,7 @@ export function App(): React.ReactElement {
         sessions={sessions}
         onSelectSession={handleSelectSession}
         onAttachSession={handleAttachSession}
+        onDeleteSession={handleDeleteSession}
         onCreateSession={handleCreateSession}
         onRefresh={refreshSessions}
         onExit={exit}

src/tui/components/HelpOverlay.tsx

@@ -24,6 +24,7 @@ const SHORTCUT_GROUPS: ShortcutGroup[] = [
       { key: '\u2191/\u2193', description: 'Navigate session 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: 'q', description: 'Quit' },

src/tui/components/StartScreen.tsx

@@ -16,6 +16,7 @@ interface StartScreenProps {
   sessions: ScreenSession[];
   onSelectSession: (session: ScreenSession) => void;
   onAttachSession: (session: ScreenSession) => void;
+  onDeleteSession: (session: ScreenSession) => void;
   onCreateSession: () => void;
   onRefresh: () => void;
   onExit: () => void;
@@ -49,6 +50,7 @@ export function StartScreen({
   sessions,
   onSelectSession,
   onAttachSession,
+  onDeleteSession,
   onCreateSession,
   onRefresh,
   onExit,
@@ -56,6 +58,13 @@ export function StartScreen({
   const now = Date.now();
   const [selectedIndex, setSelectedIndex] = useState(0);
 
+  // Ensure selectedIndex is valid when sessions change
+  React.useEffect(() => {
+    if (selectedIndex >= sessions.length && sessions.length > 0) {
+      setSelectedIndex(sessions.length - 1);
+    }
+  }, [sessions.length, selectedIndex]);
+
   // Handle keyboard input for navigation
   useInput((input, key) => {
     // Arrow key navigation
@@ -79,6 +88,12 @@ export function StartScreen({
       onAttachSession(sessions[selectedIndex]);
       return;
     }
+
+    // 'd' or 'x' to delete/kill session
+    if ((input === 'd' || input === 'x') && sessions.length > 0) {
+      onDeleteSession(sessions[selectedIndex]);
+      return;
+    }
   });
 
   return (
@@ -169,6 +184,8 @@ export function StartScreen({
             <Text> View  </Text>
             <Text color="green">[a]</Text>
             <Text> Attach  </Text>
+            <Text color="red">[d]</Text>
+            <Text> Delete  </Text>
             <Text color="green">[r]</Text>
             <Text> Refresh  </Text>
             <Text color="yellow">[q]</Text>