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/StartScreen.tsx

@@ -0,0 +1,138 @@
+/**
+ * @fileoverview StartScreen component
+ *
+ * Initial screen shown when TUI launches. Displays:
+ * - List of existing screen sessions from ~/.claudeman/screens.json
+ * - Session status (alive/dead), runtime, mode
+ * - Options to select, create, or refresh sessions
+ */
+
+import React from 'react';
+import { Box, Text } from 'ink';
+import type { ScreenSession } from '../../types.js';
+
+interface StartScreenProps {
+  sessions: ScreenSession[];
+  onSelectSession: (session: ScreenSession) => void;
+  onCreateSession: () => void;
+  onRefresh: () => void;
+  onExit: () => void;
+}
+
+/**
+ * Formats duration from milliseconds to human-readable string
+ */
+function formatDuration(ms: number): string {
+  const seconds = Math.floor(ms / 1000);
+  const minutes = Math.floor(seconds / 60);
+  const hours = Math.floor(minutes / 60);
+  const days = Math.floor(hours / 24);
+
+  if (days > 0) {
+    return `${days}d ${hours % 24}h`;
+  }
+  if (hours > 0) {
+    return `${hours}h ${minutes % 60}m`;
+  }
+  if (minutes > 0) {
+    return `${minutes}m`;
+  }
+  return `${seconds}s`;
+}
+
+/**
+ * Start screen component showing session list
+ */
+export function StartScreen({
+  sessions,
+  onSelectSession,
+  onCreateSession,
+  onRefresh,
+  onExit,
+}: StartScreenProps): React.ReactElement {
+  const now = Date.now();
+
+  return (
+    <Box flexDirection="column" padding={1}>
+      {/* Header */}
+      <Box
+        borderStyle="double"
+        borderColor="cyan"
+        paddingX={2}
+        paddingY={1}
+        justifyContent="center"
+      >
+        <Text bold color="cyan">
+          Claudeman TUI
+        </Text>
+      </Box>
+
+      <Box marginY={1}>
+        <Text dimColor>Session Manager - Press ? for help</Text>
+      </Box>
+
+      {/* Session list */}
+      {sessions.length === 0 ? (
+        <Box flexDirection="column" marginY={1}>
+          <Text color="yellow">No sessions found</Text>
+          <Text dimColor>Press [n] to create a new session</Text>
+        </Box>
+      ) : (
+        <Box flexDirection="column">
+          {/* Table header */}
+          <Box marginBottom={1}>
+            <Text bold>
+              <Text color="gray">{' #  '}</Text>
+              <Text>{'NAME'.padEnd(22)}</Text>
+              <Text>{'RUNTIME'.padEnd(12)}</Text>
+              <Text>{'STATUS'.padEnd(10)}</Text>
+              <Text>{'MODE'.padEnd(10)}</Text>
+            </Text>
+          </Box>
+
+          {/* Session rows */}
+          {sessions.map((session, index) => {
+            const runtime = formatDuration(now - session.createdAt);
+            const statusColor = session.attached ? 'green' : 'red';
+            const statusIcon = session.attached ? '\u25CF' : '\u25CB';
+            const statusText = session.attached ? 'alive' : 'dead';
+            const name = (session.name || 'unnamed').slice(0, 20);
+
+            return (
+              <Box key={session.sessionId}>
+                <Text>
+                  <Text color="cyan">[{index + 1}]</Text>
+                  <Text> </Text>
+                  <Text>{name.padEnd(22)}</Text>
+                  <Text dimColor>{runtime.padEnd(12)}</Text>
+                  <Text color={statusColor}>
+                    {statusIcon} {statusText.padEnd(8)}
+                  </Text>
+                  <Text>{session.mode.padEnd(10)}</Text>
+                </Text>
+              </Box>
+            );
+          })}
+        </Box>
+      )}
+
+      {/* Footer with controls */}
+      <Box marginTop={2} flexDirection="column">
+        <Box borderStyle="single" borderColor="gray" paddingX={1}>
+          <Text>
+            <Text color="green">[n]</Text>
+            <Text> New session  </Text>
+            <Text color="green">[1-9]</Text>
+            <Text> Select  </Text>
+            <Text color="green">[r]</Text>
+            <Text> Refresh  </Text>
+            <Text color="yellow">[q]</Text>
+            <Text> Quit  </Text>
+            <Text color="blue">[?]</Text>
+            <Text> Help</Text>
+          </Text>
+        </Box>
+      </Box>
+    </Box>
+  );
+}