feat(graceful-handoff): 2.0 — migrate to skills/ with disable-model-invocation [skip-docs]

Step 1 of v2.0 plan. Hard cut from commands/ to skills/ per Anthropic
recommendation for new plugins. Frontmatter sets disable-model-invocation:
true and pins model: claude-sonnet-4-6. Docs (README, CLAUDE.md, root
README) deferred to Step 9 per plan.

README.md

@@ -92,6 +92,8 @@ v2.1 (non-breaking) replaced the hardcoded Q1–Q8 interview with a dynamic, qua
 
 v1.7 self-verifying chain (preserved): a step may not be marked `completed` unless its manifest verifies. v1.8 Opus 4.7 literalism fixes (preserved): literal Step+Manifest template, forbidden narrative headers, schema self-check.
 
+v3.1.0 (in progress) adds a `lib/`-tree of zero-dep validators (`brief-validator`, `research-validator`, `plan-validator`, `progress-validator`, `architecture-discovery`) wired into the four commands as CLI shims, plus 109 `node:test` cases and a doc-consistency invariant test. The Phase 5.5 schema self-check now runs as `node lib/validators/plan-validator.mjs --strict` instead of three `grep -cE` calls — same checks, single source of truth, machine-readable error codes. Architecture discovery treats the `ultra-cc-architect` contract as drift-WARN, never drift-FAIL. Forking the plugin? `npm test` is the readiness gate.
+
 Defense-in-depth security: plugin hooks block destructive commands and sensitive path writes, prompt-level denylist works in headless sessions, pre-execution plan scan catches dangerous commands before they run, scoped `--allowedTools` replaces `--dangerously-skip-permissions` in parallel sessions.
 
 Modes: default, brief-driven, project-scoped, research-enriched, foreground, quick, decompose, export