fix: replace game choices with searchable autocomplete

[NicholasBottone]

Adding the 26th game caused /launchserver and /hangout_create to exceed Discord's 25-choice limit, preventing command synchronization and crashing the bot during startup. Both commands now use shared searchable autocomplete, returning at most 25 matching suggestions from the full catalog.

Users can select a suggestion or submit a complete game name (case-insensitive) or valid ID. Unknown games are rejected before launching servers or creating hangout resources. Server watch messages now show the resolved game name. Biobuzz's simulator ID is corrected from 23 to 24, avoiding its collision with Override.

Adds behavior tests for search, name/ID resolution, invalid-input rejection, and game selection in both commands, plus make test and general testing instructions in the README.

Validation

• All 12 behavior tests passed with Python 3.10 and discord.py 2.2.2 (make test PYTHON=/private/tmp/xrc-autocomplete-check/bin/python).
• Syntax compilation and git diff --check passed.
• Live Discord synchronization has not been tested; API acceptance must be verified when the bot is deployed and its commands sync.