Update CLAUDE.md with soul conventions

Sync conventions from soul/conventions/ for LLM-assisted development.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: NewGraphEnvironment

CLAUDE.md

@@ -1015,7 +1015,7 @@ Skip planning for single-file edits, quick fixes, or tasks with obvious next ste
 3. **Commit the plan** — Commit the planning files before starting implementation. This is the baseline.
 4. **Work in atomic commits** — Each commit bundles code changes WITH checkbox updates in the planning files. The diff shows both what was done and the checkbox marking it done.
 5. **Code check before commit** — Run `/code-check` on staged diffs before committing. Don't mark a task done until the diff passes review.
-6. **Archive when complete** — Move `planning/active/` to `planning/archive/` via `/planning-archive`.
+6. **Archive when complete** — Move `planning/active/` to `planning/archive/` via `/planning-archive`. Write a README.md in the archive directory with a one-paragraph outcome summary and closing commit/PR ref — future sessions scan these to catch up fast.
 
 ## Atomic Commits (Critical)