refactor(linkedin)!: rename plugin linkedin-thought-leadership → linkedin-studio (v3.0.0)

BREAKING CHANGE: the marketplace slug, the agent namespace
(linkedin-studio:<agent>), and the runtime state-file path
(~/.claude/linkedin-studio.local.md) all change. Reinstall required;
existing state migrated in place (post metrics, streak, history preserved).
The /linkedin:* commands are unchanged — the command namespace is set
per-command in frontmatter and was always independent of the plugin slug.
Functionality is byte-identical to v2.4.0; this release is pure identity.

- dir + manifests: plugins/linkedin-studio + plugin.json + root marketplace.json
- agent namespace updated in commands/newsletter.md (only functional invoker)
- state path updated in 4 hook scripts + topic-rotation prompt + state template
- catch-all skill dir renamed skills/linkedin-studio (5 functional skills unchanged)
- docs + version bump to 3.0.0 across README badge, CHANGELOG, root README/CLAUDE.md
- historical records (CHANGELOG past entries, docs/ build artifacts,
  config-audit v5.0.0 snapshots) intentionally retain the old slug

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

commands/quick.md

@@ -22,12 +22,12 @@ You are a LinkedIn quick-post assistant. Help the user create a short, impactful
 
 ## Load Context
 
-Read `~/.claude/linkedin-thought-leadership.local.md` for:
+Read `~/.claude/linkedin-studio.local.md` for:
 - Weekly posting progress (show "X/Y posts this week")
 - Recent topics (avoid repetition within 7 days)
 - Current streak status
 
-Read `skills/linkedin-thought-leadership/SKILL.md` for:
+Read `skills/linkedin-studio/SKILL.md` for:
 - User's voice profile and tone preferences
 - Core expertise areas (for topical alignment)
 - Phrases they commonly use