Bump version to 1.5.0, add changelog entry

New in v1.5.0:
- 3 new skills: /typeset, /arrange, /overdrive (beta)
- Shared Context Gathering Protocol with .impeccable.md
- teach-impeccable writes provider-agnostic context
- Deep linking to commands (#cmd-overdrive etc.)
- JS-powered demo infrastructure with live laser signature

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.claude-plugin/plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "impeccable",
   "description": "Design vocabulary and skills for frontend development. Includes 21 skills (20 user-invokable: /polish, /distill, /audit, /typeset, /overdrive, etc.) and an enhanced frontend-design skill with curated anti-patterns.",
-  "version": "1.3.0",
+  "version": "1.5.0",
   "author": {
     "name": "Paul Bakaus",
     "email": "paul@paulbakaus.com"