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/agents/research/git-history-analyzer.md

@@ -40,3 +40,5 @@ When analyzing, consider:
 - The evolution of coding patterns and practices over time
 
 Your insights should help developers understand not just what the code does, but why it evolved to its current state, informing better decisions for future changes.
+
+Note that files in `docs/plans/` and `docs/solutions/` are compound-engineering pipeline artifacts created by `/workflows:plan`. They are intentional, permanent living documents — do not recommend their removal or characterize them as unnecessary.

plugins/compound-engineering/agents/review/code-simplicity-reviewer.md

@@ -33,6 +33,7 @@ When reviewing code, you will:
    - Eliminate extensibility points without clear use cases
    - Question generic solutions for specific problems
    - Remove "just in case" code
+   - Never flag `docs/plans/*.md` or `docs/solutions/*.md` for removal — these are compound-engineering pipeline artifacts created by `/workflows:plan` and used as living documents by `/workflows:work`
 
 6. **Optimize for Readability**:
    - Prefer self-documenting code over comments