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>

peptide-repo-core.php

@@ -0,0 +1,46 @@
+<?php
+/**
+ * Plugin Name: Peptide Repo Core
+ * Plugin URI:  https://peptiderepo.com
+ * Description: Canonical peptide schema — shared data layer for the peptiderepo.com ecosystem. Provides the pr_peptide CPT, dosing rows, legal status cells, AI candidate queue, disclaimer component, and JSON-LD output.
+ * Version:     0.1.0
+ * Author:      peptiderepo
+ * Author URI:  https://peptiderepo.com
+ * License:     GPL-2.0-or-later
+ * Text Domain: peptide-repo-core
+ * Requires PHP: 8.0
+ *
+ * @see ARCHITECTURE.md — Full data flow and file tree.
+ * @see CONVENTIONS.md  — Naming patterns and extension guides.
+ */
+
+declare(strict_types=1);
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+/* ── Constants ────────────────────────────────────────────────────────── */
+
+define( 'PR_CORE_VERSION', '0.1.0' );
+define( 'PR_CORE_PLUGIN_FILE', __FILE__ );
+define( 'PR_CORE_PLUGIN_DIR', plugin_dir_path( __FILE__ ) );
+define( 'PR_CORE_PLUGIN_URL', plugin_dir_url( __FILE__ ) );
+define( 'PR_CORE_TARGET_SCHEMA_VERSION', 3 );
+
+/* ── Autoloader ───────────────────────────────────────────────────────── */
+
+require_once PR_CORE_PLUGIN_DIR . 'includes/class-pr-core-autoloader.php';
+PR_Core_Autoloader::register();
+
+/* ── Activation / Deactivation ────────────────────────────────────────── */
+
+register_activation_hook( __FILE__, [ 'PR_Core_Activator', 'activate' ] );
+register_deactivation_hook( __FILE__, [ 'PR_Core_Deactivator', 'deactivate' ] );
+
+/* ── Boot ──────────────────────────────────────────────────────────────── */
+
+add_action( 'plugins_loaded', static function (): void {
+	$plugin = new PR_Core();
+	$plugin->init();
+} );