🔧(tools) migrate OpenSpec commands to opsx and skills

Replace the old .claude/commands/openspec/ structure with the new
opsx commands and skills system for better spec-driven development
workflow.

- Remove old openspec commands (apply, archive, proposal)
- Add new opsx commands with enhanced capabilities
- Add Claude Code skills for openspec workflows
- Clean up AGENTS.md and CLAUDE.md from openspec instructions
- Remove openspec/AGENTS.md (no longer needed)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

CLAUDE.md

@@ -1,21 +1,3 @@
-<!-- OPENSPEC:START -->
-# OpenSpec Instructions
-
-These instructions are for AI assistants working in this project.
-
-Always open `@/openspec/AGENTS.md` when the request:
-- Mentions planning or proposals (words like proposal, spec, change, plan)
-- Introduces new capabilities, breaking changes, architecture shifts, or big performance/security work
-- Sounds ambiguous and you need the authoritative spec before coding
-
-Use `@/openspec/AGENTS.md` to learn:
-- How to create and apply change proposals
-- Spec format and conventions
-- Project structure and guidelines
-
-Keep this managed block so 'openspec update' can refresh the instructions.
-
-<!-- OPENSPEC:END -->
 
 # CLAUDE.md
 
@@ -146,4 +128,4 @@ PHP SabreDAV server providing CalDAV protocol support, running against the share
 
 # Workflow
 - Be sure to typecheck when you're done making a series of code changes
-- Prefer running single tests, and not the whole test suite, for performance
+- Prefer running single tests, and not the whole test suite, for performance