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>

composer.json

@@ -11,8 +11,8 @@
         "phpunit/phpunit": "^10.5",
         "brain/monkey": "^2.6",
         "mockery/mockery": "^1.6",
-        "phpstan/phpstan": "^1.10",
-        "szepeviktor/phpstan-wordpress": "^1.3",
+        "phpstan/phpstan": "^2.0",
+        "szepeviktor/phpstan-wordpress": "^2.0",
         "php-stubs/wordpress-stubs": "^6.0",
         "squizlabs/php_codesniffer": "^3.7",
         "wp-coding-standards/wpcs": "^3.0"
@@ -30,7 +30,7 @@
     "scripts": {
         "test": "phpunit --configuration phpunit.xml",
         "test:coverage": "phpunit --configuration phpunit.xml --coverage-html coverage/",
-        "lint": "phpstan analyse src/ --level=6 --configuration phpstan.neon --memory-limit=1G",
+        "lint": "phpstan analyse --configuration phpstan.neon --memory-limit=1G",
         "cs": "phpcs --standard=phpcs.xml.dist",
         "cs:fix": "phpcbf --standard=phpcs.xml.dist",
         "build": "bash bin/build-zip.sh"