Improvement: protect plan files from review deletion (#142)

* fix: protect plan and solution files from review/resolve deletion

The review/resolve pipeline could flag docs/plans/*.md and
docs/solutions/*.md files for deletion, contradicting /workflows:work
which treats them as living documents.

Adds protection at three layers:
- review.md: Protected Artifacts section + synthesis filter
- code-simplicity-reviewer.md: YAGNI exception for pipeline artifacts
- resolve_todo_parallel.md: Safety check to skip/wont_fix such todos

Fixes #140

* fix: protect plan and solution files from review/resolve deletion

The review/resolve pipeline could flag docs/plans/*.md and
docs/solutions/*.md files for deletion, contradicting /workflows:work
which treats them as living documents.

Adds protection at four layers:
- review.md: Protected Artifacts section and synthesis filter
- code-simplicity-reviewer.md: YAGNI exception for pipeline artifacts
- resolve_todo_parallel.md: Skip and wont_fix todos targeting these paths
- git-history-analyzer.md: Note not to characterize them as unnecessary

Fixes #140

---------

Co-authored-by: Axl Ottle <axl@Axls-Virtual-Machine.local>

plugins/compound-engineering/commands/workflows/review.md

@@ -48,6 +48,17 @@ Ensure that the code is ready for analysis (either in worktree or on current bra
 
 </task_list>
 
+#### Protected Artifacts
+
+<protected_artifacts>
+The following paths are compound-engineering pipeline artifacts and must never be flagged for deletion, removal, or gitignore by any review agent:
+
+- `docs/plans/*.md` — Plan files created by `/workflows:plan`. These are living documents that track implementation progress (checkboxes are checked off by `/workflows:work`).
+- `docs/solutions/*.md` — Solution documents created during the pipeline.
+
+If a review agent flags any file in these directories for cleanup or removal, discard that finding during synthesis. Do not create a todo for it.
+</protected_artifacts>
+
 #### Parallel Agents to review the PR:
 
 <parallel_tasks>
@@ -207,6 +218,7 @@ Remove duplicates, prioritize by severity and impact.
 <synthesis_tasks>
 
 - [ ] Collect findings from all parallel agents
+- [ ] Discard any findings that recommend deleting or gitignoring files in `docs/plans/` or `docs/solutions/` (see Protected Artifacts above)
 - [ ] Categorize by type: security, performance, architecture, quality, etc.
 - [ ] Assign severity levels: 🔴 CRITICAL (P1), 🟡 IMPORTANT (P2), 🔵 NICE-TO-HAVE (P3)
 - [ ] Remove duplicate or overlapping findings