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/doc/SKILL.md

@@ -0,0 +1,29 @@
+---
+name: doc
+description: |
+  Full documentation audit and sync. Detects stale docs by cross-referencing
+  git history against README, CLAUDE.md, INSTALL.md, CONFIGURE.md, USAGE.md,
+  CONTRIBUTING.md, CHANGELOG.md, docs/**/*.md, and inline comments (JSDoc,
+  docstrings, rustdoc, godoc). Reports drift with commit refs, proposes fixes,
+  patches approved items.
+  Trigger: "doc", "sync docs", "audit docs", "update readme", "check documentation",
+  "are docs up to date", "documentation drift", "stale docs".
+  Replaces the old /readme skill with broader scope.
+argument-hint: [leave empty for full audit, or list specific files/docs to check]
+disable-model-invocation: false
+allowed-tools:
+  - Read
+  - Edit
+  - Write
+  - Bash
+  - Grep
+  - Glob
+---
+
+Load and follow strictly:
+- $HOME/.claude/agents/doc-syncer.md
+
+Execute the DOC SYNCER on this project.
+
+Context from the user (if any):
+$ARGUMENTS