Generate and version TypeScript declarations from _data API metadata

[Copilot]

This PR adds a deterministic path from GreyHack API JSON metadata to consumable TypeScript declarations for editor autocomplete and type-checking. It generates structured .d.ts interfaces (including method params, optionality, return unions, and docs) directly from the existing _data source of truth.

• Generator implementation

  • Added generate_types.py to parse:
    • _data/functions.json (type → methods)
    • _data/arguments.json (method params)
    • _data/returns.json (method return variants)
    • _data/descriptions.json (JSDoc text)
  • Emits types/greyscript.d.ts under declare namespace GreyHack.

• Generated API surface

  • Produces one interface per API type (including General).
  • Preserves method names from source data.
  • Maps optional args and subtype metadata (e.g., list subtypes) into TS signatures.
  • Includes JSDoc for methods where descriptions exist.

• Type-quality adjustments in generation

  • Added targeted return-type overrides for known data inconsistencies:
    • CTFEvent.player_success(): boolean
    • General.str(...): string
  • Normalizes known doc typos during JSDoc emission to keep generated output clean.

• Repository updates

  • Added /types/greyscript.d.ts (generated artifact).
  • Updated README.md with regeneration usage.
  • Added .gitignore entries for Python cache artifacts.

# regenerate declarations
python generate_types.py
# writes: types/greyscript.d.ts