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>

plugins/linkedin-studio/config/state-file.template.md

@@ -0,0 +1,61 @@
+---
+# LinkedIn Studio State
+# Auto-managed by the linkedin-studio plugin
+# Copy to ~/.claude/linkedin-studio.local.md
+
+# Posting metrics
+last_post_date: null
+first_post_date: null             # YYYY-MM-DD, set once on first post, never changed
+last_post_topic: ""              # Should match an expertise_areas value for pillar tracking
+posts_this_week: 0
+weekly_goal: 3
+current_streak: 0
+longest_streak: 0
+
+# Week tracking (ISO week)
+current_week: ""
+
+# Analytics tracking
+last_import_date: null
+last_import_week: ""
+
+# Milestone tracking
+follower_count: 0
+follower_target: 10000
+target_date: "2026-12-31"
+monthly_growth: []
+projected_10k_date: ""
+growth_rate_needed: 0
+
+# Planning
+next_planned_topic: ""
+pending_5x5x5: false
+content_series_active: ""
+
+# Profile
+expertise_areas:
+  - "general"
+  - ""
+  - ""
+  - ""
+  - ""
+---
+
+# LinkedIn Session State
+
+## Recent Posts
+
+<!-- Updated automatically by Stop hook -->
+<!-- Format: [YYYY-MM-DD] "Hook text..." (chars) - topic_area -->
+
+## Session Notes
+
+<!-- Free-form notes from sessions -->
+
+## Planned Content
+
+<!-- Upcoming posts and topics -->
+
+## Milestone Log
+
+<!-- Updated when follower_count changes. Format: [YYYY-MM] count (+delta) -->