Keep game builds independent of stale Apps Script feed

The Apple Silicon Games sheet is historical and its Apps Script JSON feed now returns a Rhino runtime deprecation page instead of records. Vercel builds failed because the game-list builder parsed that HTML as JSON and then iterated undefined data. This switches the game build to the committed Tosh snapshot, adds a parser for the existing CSV shape, records attribution beside the snapshot, and locks the deploy failure with regression coverage.

Constraint: The repo currently has unrelated dirty work, so this commit stages only the snapshot, loader, attribution note, and focused test.

Rejected: Keep using GAMES_SOURCE with retry/fallback | the endpoint is deprecated and makes deploy correctness depend on stale external infrastructure.

Rejected: Add a CSV parser dependency | the snapshot format is narrow and no new dependencies were requested.

Confidence: high

Scope-risk: narrow

Reversibility: clean

Directive: Treat docs/tosh-games-6-6-26.csv as the build input until a new canonical games data source is introduced.

Tested: pnpm run with-env vitest test/prebuild/build-game-list.test.js

Tested: pnpm run vercel-build

Author: ThatGuySam