chore: trim dead code, modularize CLI, and archive stale docs

Extract review-plan, report, quarantine, state, and config handlers into
commands/ with shared cli_helpers; remove unused exceptions and duplicate
plan summary wrappers. Archive superseded review markdown, sync docs to
517-test baseline, and fix empty series titles when only a quality tag remains.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
Co-authored-by: Cursor <cursoragent@cursor.com>

docs/archive/2026-pre-baseline/README.md

@@ -0,0 +1,13 @@
+# Archived documentation (pre-2026-05-21 baseline)
+
+These files are historical review, audit, and implementation plans from earlier refactors.
+They are **not** maintained as current project documentation.
+
+**Canonical docs (use these instead):**
+
+- `/README.md` — user guide and workflow
+- `/CHANGELOG.md` — release and refactor history
+- `/CLAUDE.md` / `/AGENTS.md` — agent/developer guidance
+- `/plans/2026-05-21-functional-code-simplification-plan-v1.md` — code simplification plan
+
+Archived on 2026-05-21 as part of the functional code trim (Phase 2).