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>

hooks/scripts/session-start.mjs

@@ -1,5 +1,5 @@
 #!/usr/bin/env node
-// SessionStart hook for linkedin-thought-leadership plugin
+// SessionStart hook for linkedin-studio plugin
 // Reads persistent state and session context, outputs JSON with additionalContext
 
 import { readFileSync, existsSync, copyFileSync, writeFileSync, mkdirSync } from 'node:fs';
@@ -12,7 +12,7 @@ import { applyWeekRollover } from './week-rollover.mjs';
 const __dirname = dirname(fileURLToPath(import.meta.url));
 const PLUGIN_ROOT = join(__dirname, '..', '..');
 const HOME = process.env.HOME || process.env.USERPROFILE || '';
-const STATE_FILE = join(HOME, '.claude', 'linkedin-thought-leadership.local.md');
+const STATE_FILE = join(HOME, '.claude', 'linkedin-studio.local.md');
 
 function extractYaml(content, key) {
   const re = new RegExp(`^${key}: *"?([^"\\n]*)"?`, 'm');
@@ -234,7 +234,7 @@ if (existsSync(STATE_FILE)) {
   }
 
   // Build context output
-  context = 'LinkedIn Thought Leadership session context loaded.\\n\\n';
+  context = 'LinkedIn Studio session context loaded.\\n\\n';
   context += `## Status\\n\`\`\`\\n${statusLine}\\n\`\`\`\\n\\n`;
 
   if (weekResetNote) context += `**${weekResetNote}**\\n\\n`;