feat: add BLOCKED + DIAGNOSE default rule and blocker report template (closes #552)

- Updated llm-project-workflow/SKILL.md with universal BLOCKED + DIAGNOSE rule, covered blocker classes, explicit prohibition of unsafe fallbacks, and proof section.
- Added templates/blocked-diagnose-report.md (standard template with all required fields).
- Updated workflows/work-issue.md, review-merge-pr.md, create-issue.md and templates/start-issue.md, review-pr.md, merge-pr.md, recover-bad-state.md to require and reference the rule at load.
- Updated docs/llm-workflow-runbooks.md to reinforce the rule for controller prompts and all workflows.
- All changes in isolated worktree branches/issue-552-blocked-diagnose. No root mutation. No unsafe fallbacks used.
- Tests (workflow + cleanup proofs): 26+ passed in run.
- git diff --check prgs/master...HEAD: clean.

skills/llm-project-workflow/templates/blocked-diagnose-report.md

@@ -46,7 +46,7 @@ Choose one or more:
 
 ---
 
-**Rule reminder (do not bypass):** 
+**Rule reminder (do not bypass):**
 If the required step is unavailable, you are BLOCKED. Diagnose using this template. Report. Stop. Unsafe fallbacks (temp scripts, direct API, MCP internals, direct imports, in-memory restoration, manual bypasses) are prohibited unless a controller has authorized them for this specific instance in a prior handoff.
 
 This report must appear in the final output / handoff before any further action.