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/class-pr-core-deactivator.php

@@ -0,0 +1,26 @@
+<?php
+declare(strict_types=1);
+
+/**
+ * Plugin deactivation handler.
+ *
+ * What: Flushes rewrite rules on deactivation (data preserved).
+ * Who calls it: register_deactivation_hook() in peptide-repo-core.php.
+ * Dependencies: None.
+ *
+ * @see peptide-repo-core.php — Registers this class on deactivation.
+ * @see uninstall.php         — Full data teardown happens on uninstall, not deactivation.
+ */
+class PR_Core_Deactivator {
+
+	/**
+	 * Run on plugin deactivation.
+	 *
+	 * Side effects: flushes rewrite rules.
+	 *
+	 * @return void
+	 */
+	public static function deactivate(): void {
+		flush_rewrite_rules();
+	}
+}