feat(kyberforge): add agent-audit skill (closes #11)

## Why

agent-author produces paired agent definition files (Claude Code .md +
Copilot .agent.md) but had no companion audit skill to validate them.
agent-audit fills that gap, giving the same structured PASS/FAIL report
that skill-audit provides for SKILL.md files.

## Implementation Notes

- validate.sh uses scope detection (walk up for plugin.json / .git) to
  locate the counterpart file and determine whether plugin-silently-ignored
  fields (hooks, mcpServers, permissionMode) should be flagged
- CC-only and silently-ignored field lists are read from
  references/field-inventory.md at runtime rather than hardcoded —
  provenance back to the research corpus; see ADR-0019
- Single-file invocation (pass either file, counterpart derived) chosen
  over directory or name+root — see ADR-0018
- 12 bats tests cover provider detection, scope detection, all FAIL paths,
  and clean-pair pass

## Impact

- kyberforge bumped to v1.1.2
- agent-author close step should be updated to reference agent-audit (#11)
- Provenance/sources chain check deferred to #60

ADR: docs/adr/0018-agent-audit-single-file-invocation.md
ADR: docs/adr/0019-agent-audit-field-inventory-reference.md
Refs: #11
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0147vXtL5sP6vorDdqXGJJU9

plugins/kyberforge/plugin.json

@@ -13,5 +13,5 @@
   "skills": [
     "skills/"
   ],
-  "version": "1.0.7"
+  "version": "1.1.2"
 }