feat(kyberforge): restructure agent-audit for plugin-scope apm agents

Validates the new single-file .apm/agents/<name>.agent.md shape agent-author
now produces at plugin/APM scope: frontmatter allowlist (name/description/
model only, from a new apm-agent-allowlist entry in field-inventory.md),
no counterpart derivation, and Pair Consistency dropped from that scope's
report entirely (nothing to pair by design). Adds a plugin/APM-scope-only
SUGGESTION when an agent's description/body implies a tool restriction or
Claude-only behavior the vendor-neutral frontmatter can no longer express
(ADR-0016).

Scope detection in both validate.sh and validate-provenance.sh switches
from a flat plugin.json/.claude-plugin/plugin.json check to a walk-up for
the nearest ancestor apm.yml with a top-level type: field, skipping
type:-less marketplace-only manifests — full switch, no dual-mode fallback
to the old plugin.json signal. validate-provenance.sh's walk-up was fixed
to match validate.sh's (it still used the old plugin.json check, and its
counterpart-merge logic was rewritten to read a single file's source_keys
instead of merging a CC+Copilot pair, since plugin/APM scope has no
counterpart). Project/user scope validation is unchanged in both scripts.

Refs: #89

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

@@ -26,3 +26,7 @@ name description tools target model disable-model-invocation user-invocable mcp-
 ## copilot-only-fields
 
 target disable-model-invocation user-invocable mcp-servers metadata
+
+## apm-agent-allowlist
+
+name description model