refactor(skills): extract skill logic into standalone agent files

Skills now delegate to agent .md files instead of embedding logic
inline. Added new agents (bugfixer, code-cleaner, commit-changer,
doc-syncer, feater, hotfixer, seo-analyzer) and new skills
(code-clean, doc, seo). Replaced /readme with /doc (broader scope).

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

skills/code-clean/SKILL.md

@@ -0,0 +1,29 @@
+---
+name: code-clean
+description: |
+  Full codebase cleanup: dead code removal, style/norm enforcement, structural
+  issues. Two-phase workflow: audit first (read-only report), then execute
+  approved fixes only. Delegates refactoring to the refactorer agent.
+  Trigger: "code-clean", "clean up the code", "remove dead code",
+  "enforce code style", "cleanup", "nettoyage du code", "code hygiene".
+  For targeted refactoring without audit → use /refactor instead.
+  For bug fixes discovered during cleanup → logged to BUGS-FOUND.md, not fixed here.
+argument-hint: <file, directory, or blank for entire project>
+disable-model-invocation: false
+allowed-tools:
+  - Read
+  - Edit
+  - Write
+  - Bash
+  - Grep
+  - Glob
+  - Agent
+  - AskUserQuestion
+---
+
+Load and follow strictly:
+- $HOME/.claude/agents/code-cleaner.md
+
+Execute the CODE-CLEANER agent on the following target:
+
+$ARGUMENTS