feat(php-src): add a BSD-licensed crate for php-src derived code

The audit in .ken/php-shim-copying.md judged 14 functions in
shirabe-php-shim (plus php_wordwrap in shirabe-external-packages) to be
line-by-line transcriptions or structural imitations of php-src. PHP's
relicensing to 3-clause BSD makes keeping them legal, but the boundary
between BSD-derived and MIT code was invisible in the source tree.

Moving them into their own crate puts the license into the build
metadata (so NOTICE generation follows the binary), makes a reverse
dependency a compile error, and encodes the origin in the module path,
which mirrors php-src's ext tree. Each function records its origin in a
fixed-format doc comment, and a new php_src_derivation_boundary linter
fails if `php-src` appears in any Rust source outside the crate.

Public paths under shirabe_php_shim:: are unchanged: functions that are
themselves derived are re-exported with `pub use`, and the wrappers that
only validate arguments stay on the MIT side.

This also resolves the duplicate wordwrap implementation.
shirabe_php_shim::wordwrap was todo!(), so SymfonyStyle::block panicked,
while shirabe-external-packages carried its own copy. Both now go
through the single port, verified against real PHP on 13 cases covering
multi-character breaks and cut.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

1 files changed, 54 insertions, 0 deletions

diff --git a/scripts/linters/src/Linters/PhpSrcDerivationBoundary.php b/scripts/linters/src/Linters/PhpSrcDerivationBoundary.php
new file mode 100644
index 00000000..6885f171
--- /dev/null
+++ b/scripts/linters/src/Linters/PhpSrcDerivationBoundary.php
@@ -0,0 +1,54 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Shirabe\Lint\Linters;
+
+use Shirabe\Lint\Linter;
+use Shirabe\Lint\Support\FileFinder;
+use Shirabe\Lint\Support\Paths;
+
+final class PhpSrcDerivationBoundary implements Linter
+{
+    private const PHP_SRC_CRATE_PREFIX = 'crates/shirabe-php-src/';
+
+    // The origin marker every php-src derived item carries, plus the bare crate name.
+    private const MARKER_RE = '/php-src/i';
+
+    public function name(): string
+    {
+        return 'php_src_derivation_boundary';
+    }
+
+    public function failureIntro(): string
+    {
+        return "Found `php-src` mentioned outside the `shirabe-php-src` crate.\n"
+            . "Code written by reading php-src is licensed under php-src's terms, not Shirabe's MIT,\n"
+            . 'so it must live in `crates/shirabe-php-src/` and be reached through that crate:';
+    }
+
+    public function check(string $rootDir, array $excludes): array
+    {
+        $errors = [];
+
+        foreach (FileFinder::rustFiles($rootDir) as $path) {
+            $relative = Paths::relativeTo($rootDir, $path);
+            if (str_starts_with($relative, self::PHP_SRC_CRATE_PREFIX)) {
+                continue;
+            }
+            if (in_array($relative, $excludes, true)) {
+                continue;
+            }
+
+            foreach (file($path) as $idx => $raw) {
+                if (!preg_match(self::MARKER_RE, $raw)) {
+                    continue;
+                }
+
+                $errors[] = "{$relative}:" . ($idx + 1) . ': ' . trim($raw);
+            }
+        }
+
+        return $errors;
+    }
+}