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/hooks/scripts/content-gatekeeper.mjs

@@ -0,0 +1,70 @@
+#!/usr/bin/env node
+// content-gatekeeper.mjs
+// Unified PreToolUse/PostToolUse gatekeeper for linkedin-studio plugin
+//
+// Replaces 4 nearly identical bash scripts:
+//   pre-content-quality-gate.sh, pre-voice-guardian.sh,
+//   pre-topic-rotation-gate.sh, post-creation-check.sh
+//
+// Usage:
+//   node content-gatekeeper.mjs <prompt-filename> [--no-session-marker]
+//
+// Arguments:
+//   prompt-filename     - Prompt file in hooks/prompts/ (e.g. content-quality-gate.md)
+//   --no-session-marker - Skip creating session-active marker (for PostToolUse)
+//
+// Exit codes:
+//   0 - Always allow (injects systemMessage or passes through)
+
+import { readFileSync, writeFileSync, mkdirSync, existsSync } from 'node:fs';
+import { join, dirname } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { isLinkedInContent } from './linkedin-content-filter.mjs';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const pluginRoot = join(__dirname, '..', '..');
+
+const promptFile = process.argv[2];
+const noSessionMarker = process.argv.includes('--no-session-marker');
+
+if (!promptFile) {
+  process.stdout.write('{}');
+  process.exit(0);
+}
+
+// Read and parse stdin JSON
+let input;
+try {
+  input = JSON.parse(readFileSync(0, 'utf-8'));
+} catch {
+  process.stdout.write('{}');
+  process.exit(0);
+}
+
+// Extract file_path from tool_input
+const toolInput = input.tool_input ?? {};
+const filePath = toolInput.file_path ?? toolInput.filePath ?? '';
+
+// Check if this is LinkedIn content
+if (!isLinkedInContent(filePath)) {
+  process.stdout.write('{}');
+  process.exit(0);
+}
+
+// Mark session as having LinkedIn content activity
+if (!noSessionMarker) {
+  const sessionDir = '/tmp/linkedin-hooks';
+  mkdirSync(sessionDir, { recursive: true });
+  writeFileSync(join(sessionDir, 'session-active'), '');
+}
+
+// Load and return prompt
+const promptPath = join(pluginRoot, 'hooks', 'prompts', promptFile);
+if (!existsSync(promptPath)) {
+  process.stdout.write('{}');
+  process.exit(0);
+}
+
+const promptContent = readFileSync(promptPath, 'utf-8');
+process.stdout.write(JSON.stringify({ systemMessage: promptContent }));
+process.exit(0);