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>

uninstall.php

@@ -0,0 +1,74 @@
+<?php
+/**
+ * Peptide Repo Core — Full data teardown on uninstall.
+ *
+ * Removes ALL plugin data: custom tables, CPT posts + meta, taxonomy terms,
+ * options, and capabilities. No orphaned data left behind.
+ *
+ * @see ARCHITECTURE.md — Section 2.9 Uninstall specification.
+ */
+
+if ( ! defined( 'WP_UNINSTALL_PLUGIN' ) ) {
+	exit;
+}
+
+global $wpdb;
+
+/* ── 1. Drop custom tables ────────────────────────────────────────────── */
+
+$tables = [
+	$wpdb->prefix . 'pr_dosing_rows',
+	$wpdb->prefix . 'pr_legal_cells',
+	$wpdb->prefix . 'pr_ai_candidate_queue',
+];
+
+foreach ( $tables as $table ) {
+	// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery, WordPress.DB.DirectDatabaseQuery.SchemaChange
+	$wpdb->query( "DROP TABLE IF EXISTS {$table}" );
+}
+
+/* ── 2. Delete all pr_peptide posts (cascade deletes meta) ────────────── */
+
+$post_ids = $wpdb->get_col(
+	"SELECT ID FROM {$wpdb->posts} WHERE post_type = 'pr_peptide'"
+);
+
+foreach ( $post_ids as $post_id ) {
+	wp_delete_post( (int) $post_id, true );
+}
+
+/* ── 3. Delete taxonomy terms ─────────────────────────────────────────── */
+
+$taxonomies = [ 'pr_peptide_category', 'pr_peptide_family' ];
+
+foreach ( $taxonomies as $taxonomy ) {
+	$terms = get_terms( [
+		'taxonomy'   => $taxonomy,
+		'hide_empty' => false,
+		'fields'     => 'ids',
+	] );
+
+	if ( is_array( $terms ) ) {
+		foreach ( $terms as $term_id ) {
+			wp_delete_term( (int) $term_id, $taxonomy );
+		}
+	}
+}
+
+/* ── 4. Delete all pr_core_ prefixed options ──────────────────────────── */
+
+// phpcs:ignore WordPress.DB.DirectDatabaseQuery.DirectQuery
+$wpdb->query(
+	"DELETE FROM {$wpdb->options} WHERE option_name LIKE 'pr\_core\_%'"
+);
+
+/* ── 5. Remove manage_peptide_content capability from all roles ────────── */
+
+$editable_roles = wp_roles()->roles;
+
+foreach ( array_keys( $editable_roles ) as $role_name ) {
+	$role = get_role( $role_name );
+	if ( $role && $role->has_cap( 'manage_peptide_content' ) ) {
+		$role->remove_cap( 'manage_peptide_content' );
+	}
+}