refactor(lint): rewrite structural linters from Ruby to PHP

Fold scripts/lint and scripts/linters/*.rb into a standalone Composer
project under scripts/linters/, matching the scripts/plugin-class-classifier/
convention. Uses no external packages, only PHP + Composer autoloading.

Verified byte-for-byte identical output against the original Ruby
implementation, both on the current repo (all linters pass) and on a
synthetic fixture exercising every violation type.

Entry point moves from `scripts/lint` to `scripts/linters/lint`.

1 files changed, 15 insertions, 0 deletions

diff --git a/scripts/linters/src/Support/Paths.php b/scripts/linters/src/Support/Paths.php
new file mode 100644
index 00000000..2e500570
--- /dev/null
+++ b/scripts/linters/src/Support/Paths.php
@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Shirabe\Lint\Support;
+
+final class Paths
+{
+    public static function relativeTo(string $rootDir, string $path): string
+    {
+        $root = rtrim($rootDir, '/') . '/';
+
+        return str_starts_with($path, $root) ? substr($path, strlen($root)) : $path;
+    }
+}