feat: add playable Blokus web UI with replay system

- Add blokus_ui package: Flask web app for human-vs-bot Blokus
- GameSession: wraps BlokusGame for human play, records move history, serializes
- RunStore: file-based JSON replay storage with save/load/list/delete
- Flask app: routes for new game, play, save, browse runs, replay
- Templates: index (new game + run browser), game (playable board), replay (step controls)
- Static: CSS (dark theme, colored cells, placement overlays) + JS (click handling, API calls)
- Add blokus_ui tests (19 tests for GameSession and RunStore)
- Update pyproject.toml with flask dependency and blokus-ui entry point
- Fix: remove unreachable dead code in BlokusGame.valid_move
- All 102 tests pass, ruff lint clean

pyproject.toml

@@ -5,12 +5,12 @@ build-backend = "setuptools.build_meta"
 [project]
 name = "blokus-gym"
 version = "0.1.0"
-description = "A Gymnasium-compatible RL environment for the board game Blokus"
+description = "A Gymnasium-compatible RL environment for the board game Blokus, with a playable web UI"
 readme = "README.md"
 requires-python = ">=3.10"
 license = {text = "MIT"}
 authors = [{name = "Blokus Gym Contributors"}]
-keywords = ["reinforcement-learning", "gymnasium", "blokus", "board-game", "pettingzoo"]
+keywords = ["reinforcement-learning", "gymnasium", "blokus", "board-game", "pettingzoo", "flask", "game-ui"]
 classifiers = [
     "Development Status :: 3 - Alpha",
     "Intended Audience :: Science/Research",
@@ -29,6 +29,7 @@ dependencies = [
 
 [project.optional-dependencies]
 render = ["matplotlib>=3.7"]
+ui = ["flask>=3.0"]
 dev = [
     "pytest>=7.4",
     "pytest-cov>=4.1",
@@ -45,6 +46,9 @@ train = [
 Homepage = "https://github.com/blokus-gym/blokus-gym"
 Documentation = "https://github.com/blokus-gym/blokus-gym#readme"
 
+[project.scripts]
+blokus-ui = "blokus_ui.app:app"
+
 [tool.setuptools.packages.find]
 where = ["src"]