feat: initial peptide-repo-core plugin (v0.1.0) — canonical schema sprint

Implements ADR-0002: canonical peptide schema as shared data layer for
the peptiderepo.com ecosystem. All Tier 1 tools (Reconstitution Calculator,
Dosage Reference, Legal Status Tracker, PSA enhancements) build on this.

Includes:
- pr_peptide CPT with REST, taxonomies, 11 meta fields
- 3 custom tables: pr_dosing_rows, pr_legal_cells, pr_ai_candidate_queue
- Sequential migration runner with schema versioning
- 4 typed DTOs and 4 repository classes (full CRUD)
- REST API (pr-core/v1): 6 endpoints (read public, write auth-gated)
- Admin UI: 3 meta boxes, custom columns, AI candidate queue page
- Shared disclaimer component (shortcode + static API)
- JSON-LD Drug schema emission on single peptide pages
- Seed data fixture (3 peptides, 10 dosing rows, 5 legal cells)
- Full teardown in uninstall.php
- CI: PHP lint 8.0-8.2, PHPCS WordPress, 300-line check

All 22 PHP files under 300 lines. Highest: peptide-cpt at 265.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

includes/admin/class-pr-core-admin.php

@@ -0,0 +1,77 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * Admin initialization and hook registration.
+ *
+ * What: Registers admin menu pages, meta boxes, and custom columns for peptides.
+ * Who calls it: PR_Core::init() when is_admin().
+ * Dependencies: PR_Core_Peptide_Metaboxes, PR_Core_Candidate_Queue_Page, PR_Core_Admin_Columns.
+ *
+ * @see admin/class-pr-core-peptide-metaboxes.php    — Dosing + legal meta boxes.
+ * @see admin/class-pr-core-candidate-queue-page.php — Candidate review screen.
+ * @see admin/class-pr-core-admin-columns.php        — Custom list-table columns.
+ */
+class PR_Core_Admin {
+
+	/**
+	 * Register all admin hooks.
+	 *
+	 * Side effects: registers add_meta_boxes, save_post, admin_menu hooks.
+	 *
+	 * @return void
+	 */
+	public function register_hooks(): void {
+		$metaboxes = new PR_Core_Peptide_Metaboxes();
+		add_action( 'add_meta_boxes', [ $metaboxes, 'add_meta_boxes' ] );
+		add_action( 'save_post_' . PR_Core_Peptide_CPT::POST_TYPE, [ $metaboxes, 'save_meta' ], 10, 2 );
+
+		$columns = new PR_Core_Admin_Columns();
+		add_filter( 'manage_' . PR_Core_Peptide_CPT::POST_TYPE . '_posts_columns', [ $columns, 'add_columns' ] );
+		add_action( 'manage_' . PR_Core_Peptide_CPT::POST_TYPE . '_posts_custom_column', [ $columns, 'render_column' ], 10, 2 );
+
+		add_action( 'admin_menu', [ $this, 'add_admin_pages' ] );
+		add_action( 'admin_enqueue_scripts', [ $this, 'enqueue_admin_styles' ] );
+	}
+
+	/**
+	 * Add the Candidate Queue submenu page under the Peptides menu.
+	 *
+	 * Side effects: registers admin menu page.
+	 *
+	 * @return void
+	 */
+	public function add_admin_pages(): void {
+		$pending_count = ( new PR_Core_Candidate_Queue_Repository() )->count_by_status( 'pending' );
+		$badge         = $pending_count > 0 ? sprintf( ' <span class="awaiting-mod">%d</span>', $pending_count ) : '';
+
+		add_submenu_page(
+			'edit.php?post_type=' . PR_Core_Peptide_CPT::POST_TYPE,
+			__( 'AI Candidate Queue', 'peptide-repo-core' ),
+			__( 'Candidate Queue', 'peptide-repo-core' ) . $badge,
+			PR_Core_Peptide_CPT::CAPABILITY,
+			'pr-core-candidates',
+			[ new PR_Core_Candidate_Queue_Page(), 'render' ]
+		);
+	}
+
+	/**
+	 * Enqueue minimal admin CSS for meta boxes.
+	 *
+	 * @param string $hook_suffix Current admin page hook.
+	 * @return void
+	 */
+	public function enqueue_admin_styles( string $hook_suffix ): void {
+		$screen = get_current_screen();
+		if ( ! $screen || PR_Core_Peptide_CPT::POST_TYPE !== $screen->post_type ) {
+			return;
+		}
+
+		wp_enqueue_style(
+			'pr-core-admin',
+			PR_CORE_PLUGIN_URL . 'assets/css/admin.css',
+			[],
+			PR_CORE_VERSION
+		);
+	}
+}