Upgrade PHPStan to 2.x and raise analysis level from 6 to 10

- Bump phpstan/phpstan ^2.0 and szepeviktor/phpstan-wordpress ^2.0
- Move the analysis level into phpstan.neon (single source) and raise it to 10
- Add Val, a runtime coercion helper that narrows untyped WordPress boundary
  values (wpdb rows, REST params, superglobals, options) with explicit checks
  instead of blind casts, plus unit tests
- Type value-object fromRow() params as stdClass (what wpdb returns) and map
  columns through Val so unexpected shapes degrade safely
- Use %i identifier placeholders for table names in all wpdb::prepare() calls
  so every query string is a literal and identifiers are escaped by WordPress;
  raises the minimum WordPress version to 6.2 where %i was introduced
- Guard wpdb::prepare() null result before wpdb::query() in updateTax()
- Fix nullable get_permalink()/strtotime() handling, list types at REST and
  capability call sites, dead null-coalescing on checked superglobals, and
  narrow get_users() results before mapping
- Register Val method names with the ValidatedSanitizedInput sniff so it
  validates the real sanitizer around each superglobal read
- Update repository unit tests for the %i placeholder arguments

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/Availability/AvailabilityEndpoint.php

@@ -5,6 +5,7 @@ namespace Unsupervised\Schedular\Availability;
 
 use Unsupervised\Schedular\Auth\RoleManager;
 use Unsupervised\Schedular\Offering\OfferingRepository;
+use Unsupervised\Schedular\Val;
 
 class AvailabilityEndpoint {
 
@@ -13,6 +14,11 @@ class AvailabilityEndpoint {
 		private OfferingRepository $offerings,
 	) {}
 
+	/**
+	 * Registers this endpoint's REST routes.
+	 *
+	 * @param non-falsy-string $route_namespace REST namespace the routes are registered under (e.g. `us-scheduler/v1`).
+	 */
 	public function registerRoutes( string $route_namespace ): void {
 		register_rest_route(
 			$route_namespace,
@@ -96,11 +102,11 @@ class AvailabilityEndpoint {
 
 	public function index( \WP_REST_Request $request ): \WP_REST_Response {
 		$slots = $this->repository->findAvailable(
-			(int) $request->get_param( 'instructor_id' ),
-			(int) $request->get_param( 'offering_id' ),
-			(int) $request->get_param( 'duration_minutes' ),
-			(string) $request->get_param( 'from' ),
-			(string) $request->get_param( 'to' ),
+			Val::int( $request->get_param( 'instructor_id' ) ),
+			Val::int( $request->get_param( 'offering_id' ) ),
+			Val::int( $request->get_param( 'duration_minutes' ) ),
+			Val::string( $request->get_param( 'from' ) ),
+			Val::string( $request->get_param( 'to' ) ),
 		);
 
 		return new \WP_REST_Response( array_map( fn( AvailabilitySlot $s ) => $s->toArray(), $slots ), 200 );
@@ -108,8 +114,8 @@ class AvailabilityEndpoint {
 
 	public function create( \WP_REST_Request $request ): \WP_REST_Response|\WP_Error {
 		$instructorId = get_current_user_id();
-		$offeringId   = absint( $request->get_param( 'offering_id' ) );
-		$duration     = absint( $request->get_param( 'duration_minutes' ) );
+		$offeringId   = absint( Val::int( $request->get_param( 'offering_id' ) ) );
+		$duration     = absint( Val::int( $request->get_param( 'duration_minutes' ) ) );
 
 		// A slot may only be tied to an offering the instructor owns, so it can
 		// never inherit another instructor's price or payment routing at booking.
@@ -120,8 +126,8 @@ class AvailabilityEndpoint {
 			}
 		}
 
-		$startDt = AvailabilitySlot::normalizeDateTime( (string) $request->get_param( 'start_dt' ) );
-		$endDt   = AvailabilitySlot::normalizeDateTime( (string) $request->get_param( 'end_dt' ) );
+		$startDt = AvailabilitySlot::normalizeDateTime( Val::string( $request->get_param( 'start_dt' ) ) );
+		$endDt   = AvailabilitySlot::normalizeDateTime( Val::string( $request->get_param( 'end_dt' ) ) );
 
 		if ( null === $startDt || null === $endDt || $endDt <= $startDt ) {
 			return new \WP_Error( 'invalid_datetime', __( 'Provide a valid start and end, with the end after the start.', 'unsupervised-schedular' ), [ 'status' => 400 ] );
@@ -136,7 +142,7 @@ class AvailabilityEndpoint {
 		);
 
 		if ( 'weekly' === $request->get_param( 'recurrence' ) ) {
-			$ids = $this->repository->createWeeklySeries( $slot, absint( $request->get_param( 'weeks' ) ) );
+			$ids = $this->repository->createWeeklySeries( $slot, absint( Val::int( $request->get_param( 'weeks' ) ) ) );
 
 			return new \WP_REST_Response( [ 'ids' => $ids ], 201 );
 		}
@@ -147,7 +153,7 @@ class AvailabilityEndpoint {
 	}
 
 	public function delete( \WP_REST_Request $request ): \WP_REST_Response|\WP_Error {
-		$id   = absint( $request->get_param( 'id' ) );
+		$id   = absint( Val::int( $request->get_param( 'id' ) ) );
 		$slot = $this->repository->findById( $id );
 
 		if ( null === $slot ) {