feat(tui): add terminal user interface with Ink

Add a full TUI for Claudeman using Ink (React for CLI):
- StartScreen: Shows existing sessions from screens.json
- TabBar: Session tabs with status indicators
- TerminalView: PTY output display with scrolling
- StatusBar: Session info and keyboard shortcuts
- HelpOverlay: Full keyboard shortcut reference

Features:
- Session discovery from ~/.claudeman/screens.json
- Tab navigation (Ctrl+Tab, Ctrl+1-9)
- Create new sessions (connects to web API)
- Kill sessions via screen commands
- Keyboard-driven navigation

Usage: claudeman tui

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

src/tui/components/TabBar.tsx

@@ -0,0 +1,70 @@
+/**
+ * @fileoverview TabBar component
+ *
+ * Horizontal tab bar showing all active sessions.
+ * Features:
+ * - Visual indication of active tab
+ * - Status indicator (idle/working)
+ * - Tab truncation for long names
+ */
+
+import React from 'react';
+import { Box, Text } from 'ink';
+import type { ScreenSession } from '../../types.js';
+
+interface TabBarProps {
+  sessions: ScreenSession[];
+  activeSessionId: string | null;
+  onSelectSession: (sessionId: string) => void;
+}
+
+/**
+ * TabBar component for session navigation
+ */
+export function TabBar({
+  sessions,
+  activeSessionId,
+}: TabBarProps): React.ReactElement {
+  if (sessions.length === 0) {
+    return (
+      <Box borderStyle="single" borderColor="gray" paddingX={1}>
+        <Text dimColor>No sessions</Text>
+      </Box>
+    );
+  }
+
+  return (
+    <Box borderStyle="single" borderColor="cyan" paddingX={1}>
+      {sessions.map((session, index) => {
+        const isActive = session.sessionId === activeSessionId;
+        const name = (session.name || 'unnamed').slice(0, 15);
+        // Status indicator: filled circle for alive, hollow for dead
+        const statusIcon = session.attached ? '\u25CF' : '\u25CB';
+        const statusColor = session.attached ? 'green' : 'red';
+
+        return (
+          <Box key={session.sessionId} marginRight={1}>
+            {isActive ? (
+              <Text backgroundColor="blue" color="white" bold>
+                {' '}
+                <Text color={statusColor}>{statusIcon}</Text> {name}{' '}
+              </Text>
+            ) : (
+              <Text>
+                {' '}
+                <Text color={statusColor}>{statusIcon}</Text>{' '}
+                <Text dimColor>{name}</Text>{' '}
+              </Text>
+            )}
+            {index < sessions.length - 1 && <Text dimColor>|</Text>}
+          </Box>
+        );
+      })}
+
+      {/* Shortcut hint */}
+      <Box flexGrow={1} justifyContent="flex-end">
+        <Text dimColor>Ctrl+Tab: switch | Ctrl+W: close</Text>
+      </Box>
+    </Box>
+  );
+}