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/linear-tools-setup/SKILL.md

@@ -0,0 +1,18 @@
+---
+name: setup
+description: This skill should be used when user encounters "Linear auth failed", "Linear OAuth error", "Linear MCP error", "Linear not working", "unauthorized", or needs help configuring Linear integration.
+---
+
+# Linear Tools Setup
+
+Run `/linear-tools:setup` to configure Linear MCP.
+
+## Quick Fixes
+
+- **OAuth failed** - Re-authenticate via `/mcp` command
+- **Unauthorized** - Check Linear workspace permissions
+- **Token expired** - Re-run OAuth flow
+
+## Don't Need Linear?
+
+Disable via `/mcp` command to prevent errors.