Add a web (browser) front-end and an example web app

[dmccoystephenson]

Summary

Adds a third front-end behind the existing BaseUserInterface contract — a browser-based web interface — plus an example app that runs the whole game in the browser. No new dependencies (Python standard library only).

• src/ui/webUserInterface.py — WebUserInterface(BaseUserInterface). The synchronous game loop is unchanged: each input primitive (showOptions, showDialogue, promptForText, timedKeyPress) publishes the current "screen" and blocks until the browser responds, via a thread-safe rendezvous (queue.Queue + a versioned screen snapshot). A daemon-thread http.server serves the page (GET /), the screen state (GET /state), and accepts responses (POST /input). showInteractiveDialogue/promptForNumber are inherited from the base, so NPC dialogue and numeric prompts work for free.
• UIType.WEB + a lazy factory branch (so console/pygame modes don't start the HTTP machinery).
• FishE(interfaceType=...) — optional, default unchanged — lets a caller pick a front-end without editing the module constant.
• examples/web_app.py — python3 examples/web_app.py, open http://127.0.0.1:8000.
• README documents it.

Test plan

• python3 -m compileall -q src clean
• SDL_VIDEODRIVER=dummy SDL_AUDIODRIVER=dummy python3 -m pytest — 198 passed
• New tests/ui/test_webUserInterface.py: implements the interface; showOptions/promptForText/promptForNumber/showDialogue/timedKeyPress round-trip via the rendezvous; invalid options ignored; and a real ephemeral-port HTTP smoke test (serves /, /state, accepts /input).
• Manual end-to-end smoke: the example app serves the page, runs the save-file manager in-browser, creates a save, and renders the in-game screen (full header) entirely over HTTP.

🤖 Generated with Claude Code

[dmccoystephenson]

Self-review:

• Scope: PASS — WebUserInterface + UIType.WEB + lazy factory branch + FishE interfaceType param + example app + README + tests.
• Dependencies: PASS — Python standard library only (http.server, queue, threading); pygame/console modes unaffected (lazy import).
• Abstraction/DRY: PASS — implements the BaseUserInterface primitives; inherits showInteractiveDialogue and promptForNumber, so dialogue/numeric input work without web-specific code.
• Tests: PASS — 198; rendezvous round-trips for every primitive + invalid-option handling + a real ephemeral-port HTTP smoke test; manual end-to-end of the example app verified.
• Safety: default front-end unchanged; no schema/persistence/save-file paths touched.
• CI: PASS.