fix: bump claude-md-progressive-disclosurer to v1.1.0 and add version bump rule

- Bump claude-md-progressive-disclosurer 1.0.1 → 1.1.0 (missed in previous commit)
- Add mandatory "Updating Existing Skills" rule to CLAUDE.md: any commit
  that modifies a skill's files MUST bump that skill's version in marketplace.json

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.claude-plugin/marketplace.json

@@ -438,7 +438,7 @@
       "description": "Optimize user CLAUDE.md files by applying progressive disclosure principles. This skill should be used when users want to reduce CLAUDE.md bloat, move detailed content to references, extract reusable patterns into skills, or improve context efficiency. Triggers include optimize CLAUDE.md, reduce CLAUDE.md size, apply progressive disclosure, or complaints about CLAUDE.md being too long",
       "source": "./",
       "strict": false,
-      "version": "1.0.1",
+      "version": "1.1.0",
       "category": "productivity",
       "keywords": [
         "claude-md",