Post-ship documentation update. Reads all project docs, cross-references the
diff, builds a Diataxis coverage map (reference/how-to/tutorial/explanation),
updates README/ARCHITECTURE/CONTRIBUTING/CLAUDE.md to match what shipped,
detects architecture diagram drift, polishes CHANGELOG voice with a sell-test
rubric, cleans up TODOS, and optionally bumps VERSION. Surfaces documentation
debt in the PR body. Use when asked to "update the docs", "sync documentation",
or "post-ship docs". Proactively suggest after a PR is merged or code is shipped. (gstack)
