Stub bundled SKILL.md; read canonical methodology from MCP resource

The bundled skill file was a frozen 542-line copy that only updated on
plugin re-release. Replace it with a thin pointer to the server-side
resource `skill://methodology`, so skill-content changes propagate
without requiring users to reinstall the plugin.

- skills/oci-deal-accelerator/SKILL.md: reduced to ~40-line stub that
  directs Codex to read skill://methodology first, with a minimal
  tool table and fallback behavior if the MCP is unreachable
- .codex-plugin/plugin.json: bump to 0.2.0 (breaking change in what
  the plugin ships; Codex treats new versions as new cache entries)
- .gitignore: ignore Codex CLI's local .codex state file

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.gitignore

@@ -11,6 +11,9 @@ Thumbs.db
 # Claude Code local settings
 .claude/settings.local.json
 
+# Codex CLI local state
+.codex
+
 # Env / secrets
 .env
 .env.*