feat(ultraplan-local): v2.3.1 — qualified slug convention for cc-architect-catalog

Resolves v2.3.0 dogfood collision: skill-factory produced a
specialized hooks-pattern.md draft that would have overwritten the
generic seed. Qualified slugs let one feature host multiple named
patterns at different abstraction levels.

Slug convention: <cc_feature>[-<qualifier>]-<layer>.md. Unqualified =
canonical baseline. Qualified = sub-pattern (e.g., hooks-observability-
pattern.md) that does not displace the baseline.

Changes:
- SKILL.md: slug convention section, coverage-table qualified column,
  matcher logic for N patterns per feature, modification rules cover
  qualified-vs-canonical choice and collision handling.
- feature-matcher: catalog map is cc_feature -> {layer -> [skills]};
  selection rules (baseline by default, qualified when justified,
  multi-skill when non-overlapping); supporting_skill accepts list.
- gap-identifier: adds pattern_count[cc_feature] to coverage audit.
- architecture-critic: supporting-skill verification — every cited
  skill name must exist in the catalog (blocker severity).
- First qualified skill: hooks-observability-pattern.md (promoted from
  .drafts/, source ai-psychosis/README.md, ngram-overlap 0.01).
- Version bump 2.3.0 -> 2.3.1 across plugin.json, badges, table, root
  CLAUDE.md, CHANGELOG.

Non-breaking: existing unqualified slugs keep working, no cc_feature
taxonomy changes, hallucination gate unchanged.

plugins/ultraplan-local/CHANGELOG.md

@@ -4,6 +4,47 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
+## [2.3.1] - 2026-04-18
+
+### Added — Qualified slug convention for cc-architect-catalog
+
+Catalog files now follow `<cc_feature>[-<qualifier>]-<layer>.md`. The
+unqualified slug (e.g., `hooks-pattern.md`) remains the canonical
+baseline for a `(feature, layer)` pair. Qualified slugs (e.g.,
+`hooks-observability-pattern.md`) cover specific sub-patterns without
+displacing the baseline.
+
+**Why.** v2.3.0 dogfood surfaced a design gap: the skill-factory
+produced a draft `hooks-pattern.md` from a specialized source (progressive-
+alert observability) that collided with the existing generic `hooks-pattern.md`
+seed. Promoting would have replaced the general pattern with a narrow
+one; discarding would have lost real catalog growth. Qualified slugs
+resolve this by letting one feature host multiple named patterns at
+different abstraction levels.
+
+**Changes.**
+
+- `skills/cc-architect-catalog/SKILL.md` — slug convention section added;
+  coverage table gains "qualified patterns" column; matcher logic
+  documented for N patterns per feature; modification rules cover
+  qualified-vs-canonical choice and slug-collision handling.
+- `agents/feature-matcher.md` — catalog map is now
+  `cc_feature → {layer → [skills]}`; new "Selecting among multiple
+  patterns per feature" section (baseline by default, qualified when
+  justified, multiple when non-overlapping, never purely cosmetic);
+  `supporting_skill` accepts one-or-more skill names.
+- `agents/gap-identifier.md` — adds `pattern_count[cc_feature]` signal
+  to the catalog coverage audit.
+- `agents/architecture-critic.md` — adds supporting-skill verification:
+  every cited skill name must exist in the catalog; blocker severity.
+- First qualified skill: `hooks-observability-pattern.md` (promoted from
+  `.drafts/`, sourced from `ai-psychosis/README.md`, ngram-overlap 0.01,
+  review_status approved).
+
+**Non-breaking.** Existing unqualified slugs keep working. No changes to
+`cc_feature` taxonomy. Hallucination gate unchanged (still validates
+against `cc_feature` values, not slugs).
+
 ## [2.3.0] - 2026-04-18
 
 ### Added — Skill-factory Fase 1 MVP (`/ultra-skill-author-local`)