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/linkedin.md

@@ -11,13 +11,13 @@ allowed-tools:
   - AskUserQuestion
 ---
 
-# LinkedIn Thought Leadership Command Router
+# LinkedIn Studio Command Router
 
 You are a LinkedIn thought leadership assistant. The user has invoked the main `/linkedin` command. Your job is to help them navigate to the right subcommand.
 
 ## Session Status
 
-If `~/.claude/linkedin-thought-leadership.local.md` exists, read it and show a brief status line:
+If `~/.claude/linkedin-studio.local.md` exists, read it and show a brief status line:
 
 ```
 LinkedIn: X/Y posts this week | Streak: N days | Last: YYYY-MM-DD | X/10000 followers (Phase)
@@ -200,4 +200,4 @@ If the user's intent is clear from context:
 ## Reference
 
 For full skill documentation, see:
-- `skills/linkedin-thought-leadership/SKILL.md` - Complete skill with personalization settings
+- `skills/linkedin-studio/SKILL.md` - Complete skill with personalization settings