chore: migrate AGENTS.md to CLAUDE.md with tag-check-before-commit rule

CLAUDE.md

@@ -1 +1,50 @@
-@AGENTS.md
+# CLAUDE.md
+
+Guide for Claude Code working with this Hugo blog.
+
+## Project Info
+
+- **Type**: Hugo static site with Vietnamese tech content
+- **Theme**: hugo-theme-stack
+- **Language**: Vietnamese (with common English tech words)
+- **Timezone**: Asia/Ho_Chi_Minh (UTC+7)
+
+## Directory Structure
+
+```
+content/post/
+└── YYYY/
+    └── MM/
+        └── DD/
+            └── index.md
+```
+
+## Starting Local Development Server
+
+```bash
+hugo server -D
+```
+
+The site will be available at `http://localhost:1313`
+
+**Options:**
+- `-D` or `--buildDrafts`: Include draft content
+- `-F` or `--buildFuture`: Include future-dated content
+- `--disableFastRender`: Full re-render on all changes
+
+---
+
+## Skills
+
+This project uses custom skills for automated workflows:
+
+- **mt-add-post**: URL processing workflow for newsletter posts
+- **mt-add-tags**: Add/update tags in Hugo post frontmatter
+
+Refer to `.claude/skills/` for skill implementations.
+
+---
+
+## Git Workflow Rules
+
+**Before any git commit**, check all staged `content/post/*/index.md` files for minimal tags. If any have only `["AI-Assisted"]` or empty tags, run the `mt-add-tags` skill on them first before committing.