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/TerminalView.tsx

@@ -0,0 +1,84 @@
+/**
+ * @fileoverview TerminalView component
+ *
+ * Displays PTY output from the active session.
+ * Features:
+ * - Scrollable viewport showing last N lines
+ * - ANSI color support (handled by Ink)
+ * - Visual border indicating focus
+ */
+
+import React, { useMemo } from 'react';
+import { Box, Text } from 'ink';
+import type { ScreenSession } from '../../types.js';
+
+interface TerminalViewProps {
+  output: string;
+  height: number;
+  session: ScreenSession | null;
+}
+
+/**
+ * TerminalView component for PTY output display
+ */
+export function TerminalView({
+  output,
+  height,
+  session,
+}: TerminalViewProps): React.ReactElement {
+  // Split output into lines and get the last N lines that fit
+  const displayLines = useMemo(() => {
+    if (!output) return [];
+
+    const lines = output.split('\n');
+    // Reserve 2 lines for border
+    const visibleLines = height - 2;
+
+    if (lines.length <= visibleLines) {
+      return lines;
+    }
+
+    // Return last N lines
+    return lines.slice(-visibleLines);
+  }, [output, height]);
+
+  if (!session) {
+    return (
+      <Box
+        flexDirection="column"
+        borderStyle="single"
+        borderColor="gray"
+        height={height}
+        paddingX={1}
+      >
+        <Box flexGrow={1} alignItems="center" justifyContent="center">
+          <Text dimColor>No session selected</Text>
+        </Box>
+      </Box>
+    );
+  }
+
+  return (
+    <Box
+      flexDirection="column"
+      borderStyle="single"
+      borderColor="green"
+      height={height}
+      paddingX={1}
+      overflow="hidden"
+    >
+      {/* Terminal content */}
+      <Box flexDirection="column" flexGrow={1}>
+        {displayLines.length === 0 ? (
+          <Text dimColor>Waiting for output...</Text>
+        ) : (
+          displayLines.map((line, index) => (
+            <Text key={index} wrap="truncate">
+              {line}
+            </Text>
+          ))
+        )}
+      </Box>
+    </Box>
+  );
+}