feat(linkedin): integrate state-updater.mjs across all commands and hooks

Replace manual YAML editing instructions with deterministic
state-updater.mjs calls in 8 content commands (post, quick, react,
pipeline, first-post, video, publish, carousel) and 2 hook prompts
(state-update-reminder, post-creation-automation). Batch.md gets note
that state updates happen at publish time.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

plugins/linkedin-thought-leadership/commands/first-post.md

@@ -145,13 +145,20 @@ Then present: "Post copied to clipboard. Go to linkedin.com, click 'Start a post
 
 ## Step 7: State Update
 
-After finalizing:
-- Set `first_post_date` to today (YYYY-MM-DD) — this is the most important update
-- Set `last_post_date` to today
-- Set `last_post_topic` to the topic
-- Set `posts_this_week` to 1 (or increment if week matches)
-- Set `current_streak` to 1
-- Add entry to "## Recent Posts"
+After finalizing, update state deterministically (this also sets `first_post_date` automatically):
+```bash
+node --input-type=module -e "
+import { writeState, updatePostTracking } from '${CLAUDE_PLUGIN_ROOT}/hooks/scripts/state-updater.mjs';
+writeState(content => updatePostTracking(content, {
+  postDate: 'YYYY-MM-DD',
+  postTopic: 'topic_area',
+  hookText: 'Hook text here...',
+  charCount: NNNN,
+  format: 'post'
+}));
+"
+```
+Replace placeholders with actual post data. `first_post_date` is set automatically when null.
 
 ## Step 8: Next Steps