feat(wordgame): add multiplayer PvP word guessing cog

[psykzz]

Summary

Adds a new wordgame cog — a multiplayer PvP word-guessing game (Wordle-style) played entirely inside Discord threads. Anyone in a guild can start a game; players compete for points by probing letters rather than racing to guess the word.

Changes

• wordgame/wordgame.py — main cog: /wordgame start [length] slash command, [p]wordgame end admin prefix command, on_message listener for in-thread guess processing, live scoreboard editing
• wordgame/game.py — pure scoring logic: compute_feedback (produces ?!- strings, Wordle-style duplicate handling), compute_score (global position-claim tracking, word bonus), word-list helpers
• wordgame/views.py — ScoreboardView with a persistent 🔚 End Game button (admin-only); survives bot restarts via stable custom_id
• wordgame/data/answers.txt — ~6k curated answer words (ENABLE list intersected with Google 10k common words, lengths 3–8)
• wordgame/data/valid_words.txt — ~80k valid-guess dictionary (full ENABLE public-domain list, lengths 3–8)

How it works

1. /wordgame start [length=5] picks a random word, posts an announcement in the channel, and creates a thread from it
2. The first message in the thread is a live scoreboard — edited after every guess
3. Players type words directly in the thread; the bot validates length + dictionary membership, scores the guess, and replies with feedback (! ? - per letter)
4. Scoring (global scope): +1 per unique correct letter, +1 position bonus if no other player has already claimed that (letter, position) pair, +2 bonus for guessing the full word
5. Max 3 guesses per player; game auto-ends when everyone is done
6. Admins can force-end via [p]wordgame end or the 🔚 button on the scoreboard
7. Game state is persisted to Red Config — active games resume after a bot restart

Testing

• Python syntax: python -m py_compile wordgame/*.py ✅
• Lint: flake8 wordgame/ --max-line-length=100 ✅
• Manual testing requires a running Red-bot instance with the cog loaded

Risk

• No external dependencies added
• No migrations required — new Config namespace (active_games per guild)
• Word lists are public-domain (ENABLE lexicon)
• on_message listener is scoped to active game threads only; no impact on other channels