feat(mappa-vitya-brainstorming): brainstorm METHODOLOGY for a mappa zone [v0.1.0]

- Behavior layer (not mechanics): how to run a storm in a mappa zone, keep
  the running-record buffer, judge maturity by criterion (not feeling), and
  route the matured result (spec → wiki concept, tasks, reviews).
- Promotion MECHANICS delegated to mappa-brainstorm-promote (not duplicated).
- Specs/knowledge → mappa wiki concept; mappa-knowledge required before wiki.
- Multiple impl tasks → paired <slug>-review + umbrella <topic>-review,
  non-implementer reviewer; ask who implements (boss does not implement).
- Notify affected projects via inbox_send.
- Reviewed by clean-context non-implementer reviewer; all findings closed
  (description → pure triggers, no 'what should we build' conflict, explicit
  promote boundary, zero-impl-task case, mandatory mappa-knowledge).
- README provenance table updated.

README.md

@@ -114,6 +114,7 @@ an explicit `adapted-from` marker in its frontmatter.
 | `find-skills` | `adapted-from: vercel-labs/skills @ c6f69c6` (MIT) — vendored copy |
 | `grilling` | `adapted-from: mattpocock/skills @ 84fdeffd` (MIT) — family collapsed to one skill (pi hides `disable-model-invocation` wrappers) |
 | `brainstorming` | `adapted-from: obra/superpowers @ 6.2.0` (MIT) — divergent phase, visual-companion dropped |
+| `mappa-vitya-brainstorming` | `author: ours` — brainstorm METHODOLOGY for a mappa zone (capture in mappa entity, maturity by criterion, spec → wiki, paired+umbrella review, ask who implements, notify); promotion mechanics delegated to `mappa-brainstorm-promote` |
 | `diagnosing-bugs` | `adapted-from: mattpocock/skills @ 84fdeffd` (MIT) + superpowers 6.2.0 concepts (Iron Law, red flags) |
 | `loop-me` | `adapted-from: mattpocock/skills @ 84fdeffd` (MIT) — workflow-spec design gate |
 | `review-kit-pi-method` | `author: ours` — pi-native spawn for clean-context review subagents |