Replace textual-serve with direct xterm.js 6.0 bundle

- Add package.json with @xterm/xterm 6.0 and all addons
- Create terminal.ts client with WebSocket protocol support
- Bundle with Bun (bun run build -> terminal.js)
- Remove textual-serve dependency from pyproject.toml
- Remove canvas monkey-patch workaround (no longer needed)
- Add scrollback support (configurable via data-scrollback)
- Update static file routing to serve from /static/
- Add Makefile targets: bundle, bundle-watch, bundle-clean
- Update tests for new static path structure

Benefits:
- Full control over xterm.js configuration
- Scrollback history now works (default 1000 lines)
- Custom font family without workarounds
- Smaller footprint (no unused Roboto Mono fonts)
- Latest xterm.js 6.0 features available

tests/test_local_server.py

@@ -3,22 +3,22 @@
 from __future__ import annotations
 
 from textual_webterm.config import App, Config
-from textual_webterm.local_server import STATIC_PATH, LocalServer
+from textual_webterm.local_server import WEBTERM_STATIC_PATH, LocalServer
 
 
 class TestLocalServer:
     """Tests for LocalServer."""
 
     def test_static_path_exists(self) -> None:
-        """Test that static path is set from textual-serve."""
-        assert STATIC_PATH is not None
-        assert STATIC_PATH.exists()
+        """Test that static path exists."""
+        assert WEBTERM_STATIC_PATH is not None
+        assert WEBTERM_STATIC_PATH.exists()
 
     def test_static_path_has_required_files(self) -> None:
         """Test that static path contains required assets."""
-        assert STATIC_PATH is not None
-        assert (STATIC_PATH / "js" / "textual.js").exists()
-        assert (STATIC_PATH / "css" / "xterm.css").exists()
+        assert WEBTERM_STATIC_PATH is not None
+        assert (WEBTERM_STATIC_PATH / "js" / "terminal.js").exists()
+        assert (WEBTERM_STATIC_PATH / "css" / "xterm.css").exists()
 
     def test_create_server(self, tmp_path) -> None:
         """Test creating a LocalServer instance."""