feat: guidelines-enforcer workflow with round-robin schedule and PR review comments

[Copilot]

Adds a new guidelines-enforcer agentic workflow that enforces .github/workflows/guidelines.md rules across the corpus and integrates it into the workshop-builder dispatch loop.

guidelines-enforcer.md

Dual-mode workflow driven by $GITHUB_EVENT_NAME:

• Schedule/dispatch: Loads round-robin state from cache-memory, selects 10–15 files per run using modular index arithmetic, checks each against all guidelines rules, and opens [guidelines]-prefixed issues (max 10, 7-day expiry, deduped by title).
• pull_request (opened/synchronize): Fetches changed .md files from the PR via gh pr view --json files, reviews each, and posts inline comments via create-pull-request-review-comment (max 20).

Both modes enforce: numbered-header prohibition, alert callout patterns, tooling-progression ordering, cron-vs-fuzzy schedule syntax in .md files, UI-first design, prerequisite scoping, checkpoint presence, and voice/tone rules.

State persisted in cache-memory:

{ "round_robin_index": 42, "files_reviewed": [...], "last_run": "2026-07-15T..." }

workshop-builder.md

• Added guidelines-enforcer to dispatch-workflow allowlist and eligibility table (nodes ≥ 3, cooldown 24 h).
• Appended to Tier A priority list and focus-hint routing ("guidelines", "rules", "enforce").

Lock files regenerated via gh aw compile (0 errors, 0 warnings).