* chore(flake): simplify nix build and add ci validation
- Replace dynamic pnpm-workspace.yaml parsing with hardcoded workspacePaths
and workspaceNames to reduce format assumptions
- Remove update-pnpm-deps script and kimi-code-pnpm-deps package; use
lib.fakeHash for standard hash mismatch workflow
- Remove nodejs_latest fallback in nodejsFor, hardcode to nodejs_24
- Add nix-build CI workflow that posts hash-mismatch details to PR comments
- Remove unused Nix installation step from release.yml
- Add workspace maintenance note to AGENTS.md
