feat(kyberforge): improve agent-audit skill with platform-accurate checks and description quality reference

- Fix validate.sh: remove incorrect name==stem check for CC files (CC docs say filename need not match name field); keep check for Copilot CLI only
- Fix validate.sh: plugin scope detection now checks both plugin.json and .claude-plugin/plugin.json
- Fix validate.sh: Copilot cloud/IDE agents (.github/copilot/agents/) have name as optional; path-based guard added
- Add validate.sh checks: Copilot body length >30,000 chars (SUGGESTION), Copilot-only fields in CC files (FAIL), subagent-unavailable tools in tools field (SUGGESTION)
- Add references/description-quality.md as conditional escape hatch for borderline description findings
- SKILL.md: name five audit dimensions in description; sharpen indirect-trigger phrasing
- SKILL.md: label pair-mandate as kyberforge project convention, not platform requirement
- SKILL.md: scope redundant name-match/body-empty checks to manual fallback only
- SKILL.md: add conditional reference to description-quality.md; update provider-safety description for new check categories; fix plugin scope gotcha to mention .claude-plugin/plugin.json
- SKILL.md: add INFO tier to result block template
- Add source_keys frontmatter to references/README.md; update sources.md to add description-quality.md to contributing files

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0147vXtL5sP6vorDdqXGJJU9

plugins/kyberforge/skills/agent-audit/references/field-inventory.md

@@ -22,3 +22,7 @@ hooks mcpServers permissionMode
 ## copilot-fields
 
 name description tools target model disable-model-invocation user-invocable mcp-servers metadata
+
+## copilot-only-fields
+
+target disable-model-invocation user-invocable mcp-servers metadata