Add comprehensive skills, agents, commands collection

- Added 44 external skills from obra/superpowers, ui-ux-pro-max-skill, claude-codex-settings
- Added 8 autonomous agents (commit-creator, pr-creator, pr-reviewer, etc.)
- Added 23 slash commands for Git/GitHub, setup, and plugin development
- Added hooks for code formatting, notifications, and validation
- Added MCP configurations for Azure, GCloud, Supabase, MongoDB, etc.
- Added awesome-openclaw-skills registry (3,002 skills referenced)
- Updated comprehensive README with full documentation

Sources:
- github.com/obra/superpowers (14 skills)
- github.com/nextlevelbuilder/ui-ux-pro-max-skill (1 skill)
- github.com/fcakyon/claude-codex-settings (29 skills, 8 agents, 23 commands)
- github.com/VoltAgent/awesome-openclaw-skills (registry)
- skills.sh (reference)
- buildwithclaude.com (reference)

skills/external/slack-tools-setup/SKILL.md

@@ -0,0 +1,18 @@
+---
+name: setup
+description: This skill should be used when user encounters "Slack MCP error", "invalid_auth", "missing_scope", "Slack not working", "Slack token invalid", "channel_not_found", or needs help configuring Slack integration.
+---
+
+# Slack Tools Setup
+
+Run `/slack-tools:setup` to configure Slack MCP.
+
+## Quick Fixes
+
+- **invalid_auth** - Token expired, regenerate at api.slack.com
+- **missing_scope** - Re-install Slack app with required scopes
+- **channel_not_found** - Bot not invited to channel
+
+## Don't Need Slack?
+
+Disable via `/mcp` command to prevent errors.