fix(ci): install eslint deps + strip ChatGPT compat claim

[tattarw]

Two fixes:

1. Make CI green (closes #128)
The npm run lint --if-present step calls eslint src --ext .ts from package.json, but eslint was never installed. Every CI run on main has been failing on this.

Fix:

• Add eslint@^8.57, @typescript-eslint/parser@^7.18, @typescript-eslint/eslint-plugin@^7.18 to devDependencies.
• Switch lint script to eslint src (flat config supersedes --ext).
• Add eslint.config.mjs with a minimal TS-aware ruleset.

2. Strip ChatGPT compatibility claim (part of #133)
README L12 pull-quote claimed Claude/Cursor/ChatGPT support. ChatGPT does not run stdio MCP servers, so that claim is incorrect. Replaced with the accurate "Claude, Cursor, Windsurf, or any MCP-compatible host" phrasing.

Deliberately NOT changed:

• Repo description (also says ChatGPT) — needs Settings edit, not a PR.
• README L22 verdict enum (PROCEED / DUE_DILIGENCE / ITERATE / ABANDON) — left for the enum-cascade PR (#126).
• Tool naming: spec ↔ README already aligned on verify_brand_name.