docs: move ACP checklist into packages/acp

Co-locate the ACP feature support checklist with the bridge package
(packages/acp/acp-feature-support.md) and rewrite its relative links for
the new depth. Broaden the doc-sync globs (doc-typecheck, verify-md-wrap,
verify-md-links) from packages/*/README.md to packages/*/*.md so a
package-level doc beyond the README stays under the drift gates, and
update the AGENTS.md prose describing that scope.

scripts/doc-typecheck.ts

@@ -97,7 +97,7 @@ function tempTsconfig(): string {
   })
 }
 
-const markdownGlobs = ['README.md', 'docs/**/*.md', 'packages/*/README.md']
+const markdownGlobs = ['README.md', 'docs/**/*.md', 'packages/*/*.md']
 
 const files: string[] = []
 for (const pattern of markdownGlobs) {