ci: adopt reusable CI + 300-line compliance for v4.7.0

- Replace per-repo CI jobs with thin reusable caller
  (peptide-e2e ci.yml@main; tests:stubs, has_js:true)
- Add permissions: contents: write (required for phpcbf auto-commit)
- deploy.yml: drop file-existence + PHP-syntax redundancy; keep PSA_VERSION check
- class-psa-admin.php: remove 37 dead backward-compat proxy lines (327→290)
- class-psa-ai-generator.php: remove 17 dead backward-compat proxy lines (309→292)
- class-psa-search.php: remove 13 dead backward-compat proxy lines (307→294)
  All three files now comply with the estate 300-line rule.
  Zero external callers of removed methods confirmed.
- package.json / package-lock.json: minimal npm manifest for lint-js npm ci step
- ARCHITECTURE.md: update ci.yml description
- PSA_VERSION: sync constant (was 4.5.0) with header (was 4.6.0) → both 4.7.0

Agent-Session: claude-sonnet-4-6-adopt-ci-20260616

includes/class-psa-search.php

@@ -291,17 +291,4 @@ class PSA_Search {
 		);
 	}
 
-	// ── Backward-compatible proxies ─────────────────────────────────────
-
-	/** @see PSA_Search_Handler::ajax_search() */
-	public static function ajax_search(): void {
-		PSA_Search_Handler::ajax_search(); }
-
-	/** @see PSA_Search_Handler::create_pending_placeholder() */
-	public static function create_pending_placeholder( string $peptide_name ) {
-		return PSA_Search_Handler::create_pending_placeholder( $peptide_name ); }
-
-	/** @see PSA_Search_Handler::schedule_background_generation() */
-	public static function schedule_background_generation( int $post_id, string $peptide_name ): void {
-		PSA_Search_Handler::schedule_background_generation( $post_id, $peptide_name ); }
 }