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/skills/cc-architect-catalog/SKILL.md

@@ -83,32 +83,70 @@ skill-factory output will start as `pending` (channel 2) or
 If a future skill covers a feature not in this list, add the row above
 and surface the extension in the relevant CHANGELOG entry.
 
+## Slug convention
+
+Skill filenames follow this pattern:
+
+```
+<cc_feature>[-<qualifier>]-<layer>.md
+```
+
+- **Unqualified slug** (`<feature>-<layer>.md`) — the baseline/canonical
+  entry for that (feature, layer) pair. One per pair. Example:
+  `hooks-pattern.md` = generic hook shapes and pitfalls.
+- **Qualified slug** (`<feature>-<qualifier>-<layer>.md`) — a
+  specialized variant covering one specific sub-pattern or use-case.
+  Zero-or-more per pair. Example: `hooks-observability-pattern.md` =
+  progressive-alert observability pattern specifically.
+
+Qualifiers exist because one CC feature can support multiple
+non-overlapping patterns at different abstraction levels. Forcing
+everything into a single `<feature>-<layer>.md` either bloats the
+canonical entry or loses useful specialization. Qualified slugs let the
+catalog grow with concrete, named patterns without displacing the
+baseline.
+
+`feature-matcher` treats all skills with the same `cc_feature` + `layer`
+as candidates and picks the most relevant to the brief (or proposes
+several if they cover different aspects). See "How `feature-matcher`
+uses this file" below.
+
 ## Current seed coverage (v2.3.0 — see .drafts/ for skill-factory output)
 
-| Feature | reference | pattern | decision |
-|---------|-----------|---------|----------|
-| hooks | hooks-reference | hooks-pattern | — |
-| subagents | subagents-reference | subagents-pattern | — |
-| skills | skills-reference | — | — |
-| output-styles | output-styles-reference | — | — |
-| mcp | mcp-reference | — | — |
-| plan-mode | plan-mode-reference | — | — |
-| worktrees | worktrees-reference | — | — |
-| background-agents | background-agents-reference | — | — |
+| Feature | reference | pattern | qualified patterns | decision |
+|---------|-----------|---------|--------------------|----------|
+| hooks | hooks-reference | hooks-pattern | hooks-observability-pattern | — |
+| subagents | subagents-reference | subagents-pattern | — | — |
+| skills | skills-reference | — | — | — |
+| output-styles | output-styles-reference | — | — | — |
+| mcp | mcp-reference | — | — | — |
+| plan-mode | plan-mode-reference | — | — | — |
+| worktrees | worktrees-reference | — | — | — |
+| background-agents | background-agents-reference | — | — | — |
 
-Total: 10 seed skills, 8 features, 2 layers. Decision-layer is
+Total: 11 seed skills, 8 features, 2 layers. Decision-layer is
 intentionally empty — decisions cross features and require broader
 synthesis than a single seed pass can provide. Skill-factory populates
 decision-layer later.
 
 ## How `feature-matcher` uses this file
 
-1. Read this file to learn the `cc_feature` taxonomy.
+1. Read this file to learn the `cc_feature` taxonomy and slug convention.
 2. Glob the directory for `*.md` files (excluding SKILL.md).
 3. Parse each skill's frontmatter.
 4. For each feature mentioned in the brief or research, match against
-   `cc_feature` field. Prefer `pattern` over `reference` when both exist
-   (pattern is richer).
+   `cc_feature` field. Build the candidate set per feature, grouped by
+   layer. Selection rules:
+   - **Layer preference:** prefer `pattern` over `reference` when both
+     exist (pattern is richer).
+   - **Multiple patterns per feature:** when two or more pattern-layer
+     skills share the same `cc_feature`, read each `description` and
+     pick the one(s) most relevant to the brief. If two cover
+     non-overlapping aspects that both apply, propose both with clear
+     rationale. Prefer the unqualified baseline (`<feature>-pattern.md`)
+     when the brief does not specifically justify a qualified variant.
+   - **Be explicit:** name the chosen skill in `supporting_skill` so
+     `architecture-critic` can verify the match.
 5. When no skill exists for a mentioned feature, fall back to the
    hardcoded minimum-list inside the `feature-matcher` prompt and mark
    the gap in stats (`fallback_used: true`).
@@ -132,9 +170,24 @@ decision-layer later.
 
 ## Modification rules
 
-- Adding a new skill: create `<feature>-<layer>.md` with the frontmatter
-  above and bump the coverage table in this file.
-- Renaming `cc_feature` values: update both this file AND every skill
-  using the old value in the same commit.
-- Removing a skill: document in CHANGELOG under the version that drops
-  it.
+- **Adding a canonical skill:** create `<feature>-<layer>.md` with the
+  frontmatter contract above. Bump the coverage table in this file.
+- **Adding a qualified pattern skill:** create
+  `<feature>-<qualifier>-<layer>.md` when the new pattern covers a
+  distinct sub-case that does not belong in the unqualified baseline.
+  The qualifier MUST be kebab-case and descriptive (e.g.,
+  `observability`, `migration`, `multi-tenant`). Add it to the
+  "qualified patterns" column in the coverage table.
+- **Choosing qualified vs. canonical:** if no unqualified skill exists
+  yet for a `(feature, layer)` pair, the new skill SHOULD be the
+  unqualified baseline — don't ship a qualified skill without a
+  canonical one, because `feature-matcher` prefers baseline when the
+  brief has no specific justification for a variant.
+- **Renaming `cc_feature` values:** update both this file AND every
+  skill using the old value in the same commit.
+- **Removing a skill:** document in CHANGELOG under the version that
+  drops it.
+- **Slug collision:** two skills with the same slug are a hard error.
+  Skill-factory (`/ultra-skill-author-local`) must refuse to promote a
+  draft that would overwrite an approved skill. Collision is resolved
+  either by qualifying the new slug or by revising the baseline.