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/import.md

@@ -222,7 +222,7 @@ Run /linkedin:report (period: 4w)
 
 `/linkedin:report` will:
 
-1. Read `expertise_areas` from `~/.claude/linkedin-thought-leadership.local.md`
+1. Read `expertise_areas` from `~/.claude/linkedin-studio.local.md`
 2. Call `trends` for impressions and engagement_rate over the last 4 weeks:
    ```bash
    ANALYTICS_ROOT="${CLAUDE_PLUGIN_ROOT}/assets/analytics" node --import tsx "${CLAUDE_PLUGIN_ROOT}/scripts/analytics/src/cli.ts" trends --period 4w --metric impressions
@@ -241,7 +241,7 @@ manually when analytics are ready."
 After successful import and analysis, update the state file:
 
 ```
-Read ~/.claude/linkedin-thought-leadership.local.md
+Read ~/.claude/linkedin-studio.local.md
 Set last_import_date to today (YYYY-MM-DD)
 Set last_import_week to current ISO week (YYYY-WXX)
 Write the updated state file