feat(event-submission): URL-based artist tour import — auto-create artist-scoped pipeline (#322)

Implements the DME side of extrachill-events#320. Adds a moderation
queue (`artist_url_submissions` under $wpdb->base_prefix), four
abilities, four REST routes, and an admin moderation screen.

Abilities (`inc/Abilities/ArtistUrlImportAbilities.php`):

- `data-machine-events/preview-artist-url` — non-destructive probe
  via UniversalWebScraper. Returns detected format, event count,
  preview list, and a suggested artist (term ID if a similar_text
  fuzzy match clears 85%, name otherwise). Logged-in users only.
- `data-machine-events/submit-artist-url` — re-probes server-side
  (never trusts client detection) and inserts a row in
  `pending_review` (or `scraping_failed`). Logged-in users only.
- `data-machine-events/approve-artist-url-submission` — admin only.
  Resolves the artist term (existing id, new name + wp_insert_term,
  or the submission's suggested term). Creates pipeline+flow via
  `datamachine/create-pipeline` + `datamachine/create-flow` mirroring
  the CityAbilities pattern, with universal_web_scraper handler.
  Triggers an immediate first run via `datamachine/run-flow`.
- `data-machine-events/reject-artist-url-submission` — admin only.
  Marks the row rejected with an optional reason.

SelectionMode alignment: the upsert step pins
`taxonomy_artist_selection = (string) $artist_term_id` (PRE_SELECTED)
and uses `SelectionMode::AI_DECIDES` constants by class reference for
venue/location/festival, `SelectionMode::SKIP` for promoter, category,
post_tag — no bare strings (#320 requirement).

Dedupe: SHA-256 over a normalized URL (lowercased scheme/host,
fragment stripped, trailing slash trimmed except root, default ports
removed). UNIQUE KEY on url_hash; duplicate preview/submit returns
`url_already_tracked`.

REST: `POST /wp-json/datamachine/v1/artist-url/{preview,submit,
{id}/approve,{id}/reject}`. Preview and submit reject direct-browser
navigations (no XHR / JSON Accept header → 404), in the spirit of

Admin moderation UI (`inc/Admin/ArtistUrlSubmissionsAdmin.php`): adds
"Artist URL Imports" under Events. Tabs filter by status (pending
review, approved, rejected, failed scrapes), inline forms for approve
(artist term id OR new name + schedule) and reject (reason). Forms
post to admin-post.php with nonces and delegate to the abilities.

Tests (`tests/Unit/ArtistUrlSubmissionsTableTest.php`,
`tests/Unit/ArtistUrlImportAbilitiesTest.php`): URL normalization,
url_hash dedupe, table CRUD, preview/submit rejection paths,
`artist_required` error from approve when no artist input is
provided, reject sets status + reason. Approve's pipeline-creation
integration is covered by curl verification against a live install
(matrix in the PR body) — recreating Data Machine core abilities in
isolated unit tests would be fake coverage.

The extrachill-events side (form change consuming preview + submit
abilities) ships separately once this merges.

Co-authored-by: homeboy-ci[bot] <266378653+homeboy-ci[bot]@users.noreply.github.com>

Author: chubes4

data-machine-events.php

@@ -62,6 +62,10 @@ function data_machine_events_sanitize_query_params( $value ) {
 require_once DATA_MACHINE_EVENTS_PLUGIN_DIR . 'inc/Core/event-dates-sync.php';
 require_once DATA_MACHINE_EVENTS_PLUGIN_DIR . 'inc/Core/EventDatesTable.php';
 
+// Artist URL Submissions table (moderation queue for the #320 import flow).
+require_once DATA_MACHINE_EVENTS_PLUGIN_DIR . 'inc/Core/ArtistUrlSubmissionsTable.php';
+add_action( 'plugins_loaded', array( \DataMachineEvents\Core\ArtistUrlSubmissionsTable::class, 'maybe_install' ), 20 );
+
 // Global alias — event-dates-sync.php is namespaced so this makes the public API accessible globally.
 if ( ! function_exists( 'datamachine_get_event_dates' ) ) {
 	/**
@@ -234,6 +238,11 @@ public function init() {
 			if ( class_exists( 'DataMachineEvents\\Admin\\Settings_Page' ) ) {
 				new \DataMachineEvents\Admin\Settings_Page();
 			}
+
+			// Artist URL Submissions moderation queue (extrachill-events#320).
+			if ( class_exists( 'DataMachineEvents\\Admin\\ArtistUrlSubmissionsAdmin' ) ) {
+				new \DataMachineEvents\Admin\ArtistUrlSubmissionsAdmin();
+			}
 		}
 
 		add_action( 'init', array( $this, 'init_data_machine_integration' ), 25 );
@@ -484,6 +493,11 @@ function ( array $templates ): array {
 			new \DataMachineEvents\Abilities\MergedBillDecideAbilities();
 		}
 
+		if ( file_exists( DATA_MACHINE_EVENTS_PLUGIN_DIR . 'inc/Abilities/ArtistUrlImportAbilities.php' ) ) {
+			require_once DATA_MACHINE_EVENTS_PLUGIN_DIR . 'inc/Abilities/ArtistUrlImportAbilities.php';
+			new \DataMachineEvents\Abilities\ArtistUrlImportAbilities();
+		}
+
 		// Chat tools for the merged-bill agent decision step (issue #256).
 		if ( class_exists( 'DataMachineEvents\\Api\\Chat\\Tools\\MergedBillInspect' ) ) {
 			new \DataMachineEvents\Api\Chat\Tools\MergedBillInspect();
@@ -606,6 +620,7 @@ public function enqueue_admin_assets( $hook ) {
 
 	public function activate() {
 		\DataMachineEvents\Core\EventDatesTable::create_table();
+		\DataMachineEvents\Core\ArtistUrlSubmissionsTable::create_table();
 		$this->register_post_types();
 		$this->register_taxonomies();
 		flush_rewrite_rules();