docs(ultraplan-local): v2.3.0 — skill-factory Fase 1

Doc sync for /ultra-skill-author-local release:

- CHANGELOG.md: 2.3.0 section above 2.2.0 with full feature narrative,
  pipeline diagram, non-goals, new files list, new stats file
- README.md: command table row + new ## /ultra-skill-author-local section
  describing pipeline, modes, IP-hygiene utility, non-goals
- CLAUDE.md: row in Commands table (committed in Step 1)
- ../../README.md: bumped ultraplan-local row v2.2.0 → v2.3.0,
  expanded division-of-labor with sixth bullet for /ultra-skill-author-local,
  added v2.3 narrative paragraph

Plan: .claude/projects/2026-04-18-skill-factory-fase-1-mvp/plan.md (step 12)

plugins/ultraplan-local/CHANGELOG.md

@@ -4,6 +4,71 @@ 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/).
 
+## [2.3.0] - 2026-04-18
+
+### Added — Skill-factory Fase 1 MVP (`/ultra-skill-author-local`)
+
+Manual one-skill-at-a-time generator for the `cc-architect-catalog`.
+Channel 2 of the skill-factory strategy: a curated local source enters,
+one draft skill exits in `skills/cc-architect-catalog/.drafts/`, with
+n-gram containment scored against the source and stamped into the
+draft frontmatter (or the draft is deleted when overlap is too high).
+
+**Why now.** `/ultra-cc-architect-local` (v2.2.0) enforces a
+hallucination gate that only permits feature proposals backed by the
+catalog. With 10 seed skills covering 8 features × 2 layers, the
+`feature-matcher` rarely finds a match and silently produces empty
+proposals. Fase 1 unblocks catalog growth without spinning up
+automation: one source, one draft, manual review, manual `mv` for
+promotion.
+
+**Pipeline.** Sequential, no retry, no parallelism:
+
+```
+/ultra-skill-author-local <source>
+  → concept-extractor (sonnet, JSON output, gap-class C/D + cc_feature gate)
+  → skill-drafter (sonnet, .drafts/<slug>.md with 9-field frontmatter)
+  → ip-hygiene-checker (sonnet, runs scripts/ngram-overlap.mjs)
+      verdict accepted/needs-review → stamp ngram_overlap_score
+      verdict rejected               → rm draft (no preservation)
+```
+
+**IP-hygiene utility.** Pure Node stdlib. Word-5-gram containment
+similarity (asymmetric draft⊆source) plus longest-consecutive-shingle-
+run secondary signal. Verdict bands: accepted (<0.15 AND <8),
+needs-review (mid), rejected (≥0.35 OR ≥15). Short-text fallback to
+n=4 when min(words) <500. CLI emits JSON.
+
+**Calibration fixtures.** Three source/draft pairs in
+`tests/fixtures/skill-factory/` pin the verdict bands against
+representative prose: accepted (containment 0.014), needs-review
+(0.211), rejected (0.676). Re-verify any threshold change against
+these fixtures.
+
+**New files:**
+
+- `commands/ultra-skill-author-local.md`
+- `agents/skill-author-orchestrator.md` (opus)
+- `agents/concept-extractor.md` (sonnet)
+- `agents/skill-drafter.md` (sonnet)
+- `agents/ip-hygiene-checker.md` (sonnet)
+- `scripts/ngram-overlap.mjs` + `scripts/ngram-overlap.test.mjs`
+- `skills/cc-architect-catalog/.drafts/.gitkeep`
+- `tests/fixtures/skill-factory/{source,draft}-{accepted,needs-review,rejected}.md`
+- `tests/fixtures/skill-factory/README.md`
+
+**Non-goals (explicit, Fase 1):**
+
+- No automation, cron, or watcher
+- No CC changelog diffing or auto-research
+- No batch processing or review command
+- No decision-layer skills (cross-feature comparison is Fase 2+)
+- No URL or remote sources — local files only
+- Manual `mv` from `.drafts/` to catalog root is the promotion mechanism
+
+**New stats file:**
+`${CLAUDE_PLUGIN_DATA}/ultra-skill-author-local-stats.jsonl`.
+
 ## [2.2.0] - 2026-04-18
 
 ### Added — `/ultra-cc-architect-local` optional pipeline step