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>

scripts/test-runner.sh

@@ -1,5 +1,5 @@
 #!/bin/bash
-# LinkedIn Thought Leadership Plugin — Structure Validator
+# LinkedIn Studio Plugin — Structure Validator
 # Validates file existence, frontmatter format, and router completeness
 # Usage: bash scripts/test-runner.sh
 
@@ -21,7 +21,7 @@ fail() { echo -e "${RED}✗${NC} $1"; FAIL=$((FAIL + 1)); }
 warn() { echo -e "${YELLOW}⚠${NC} $1"; WARN=$((WARN + 1)); }
 
 echo "================================================"
-echo "LinkedIn Thought Leadership Plugin — Structure Validator"
+echo "LinkedIn Studio Plugin — Structure Validator"
 echo "Plugin root: $PLUGIN_ROOT"
 echo "================================================"
 echo ""
@@ -129,7 +129,7 @@ echo ""
 # --- Section 5: Skill Files ---
 echo "--- Skill Files ---"
 
-for skill in "linkedin-thought-leadership" "linkedin-content-creation" "linkedin-analytics" "linkedin-strategy" "linkedin-networking" "linkedin-voice"; do
+for skill in "linkedin-studio" "linkedin-content-creation" "linkedin-analytics" "linkedin-strategy" "linkedin-networking" "linkedin-voice"; do
   f="skills/${skill}.md"
   if [ -f "$PLUGIN_ROOT/$f" ]; then
     pass "$f exists"