feat(php-rpc): embed the Composer PHP runtime in the executable

Plugins and scripts need the real `Composer\` classes and the packages
Composer depends on, which so far came from a checkout found through
SHIRABE_COMPOSER_PHP_DIR or a path next to the workspace. Neither exists
for a distributed binary.

The build script now archives those PHP sources into a phar the way
Compiler.php does and the executable carries it. The worker maps it with
Phar::loadPhar and reads a content-addressed sentinel back to tell a
bundle it can use from one it cannot; where its PHP cannot open the phar,
the bundle is unpacked once into the cache directory and autoloaded from
there. SHIRABE_COMPOSER_PHP_DIR still overrides both for development.

PHP locates a phar's manifest by the first __HALT_COMPILER(); token in
the file, so the executable must hold no other copy of it: phar.rs builds
the token at run time, and a linter keeps further literals out of the
sources that reach the binary.

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

2 files changed, 83 insertions, 0 deletions

diff --git a/scripts/linters/lint b/scripts/linters/lint
index 5f59945d..e90c3e0c 100755
--- a/scripts/linters/lint
+++ b/scripts/linters/lint
@@ -11,6 +11,7 @@ use Shirabe\Lint\Linters\NoBannedUse;
 use Shirabe\Lint\Linters\NoDecorativeSectionComment;
 use Shirabe\Lint\Linters\NoExceptionDowncast;
 use Shirabe\Lint\Linters\NoFormatTrailingComma;
+use Shirabe\Lint\Linters\NoHaltCompilerLiteral;
 use Shirabe\Lint\Linters\NoModRs;
 use Shirabe\Lint\Linters\NoStdCollectionsMaps;
 use Shirabe\Lint\Linters\NoUseAsAlias;
@@ -39,6 +40,9 @@ $runner = new Runner($rootDir, [
         'crates/shirabe/src/package/loader/root_package_loader.rs',
         'crates/shirabe-spdx-licenses/src/spdx_licenses.rs',
     ]],
+    [new NoHaltCompilerLiteral(), [
+        'crates/shirabe-php-rpc/build.rs',
+    ]],
     [new NoModRs(), []],
     [new NoStdCollectionsMaps(), []],
     [new NoUseAsAlias(), []],
diff --git a/scripts/linters/src/Linters/NoHaltCompilerLiteral.php b/scripts/linters/src/Linters/NoHaltCompilerLiteral.php
new file mode 100644
index 00000000..30520ff7
--- /dev/null
+++ b/scripts/linters/src/Linters/NoHaltCompilerLiteral.php
@@ -0,0 +1,79 @@
+<?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 NoHaltCompilerLiteral implements Linter
+{
+    // Assembled so that this file does not contain what it looks for.
+    private const TOKEN = '__' . 'HALT_COMPILER();';
+
+    public function name(): string
+    {
+        return 'no_halt_compiler_literal';
+    }
+
+    public function failureIntro(): string
+    {
+        return "Found a literal `" . self::TOKEN . "`.\n"
+            . "The executable carries the Composer runtime bundle as a phar that PHP finds by\n"
+            . "scanning for the first occurrence of that token, and every literal here ends up in\n"
+            . "the same binary, so an earlier one shadows the bundle. Build the token at run time\n"
+            . "instead — see "
+            . '`halt_compiler_token` in `crates/shirabe-php-shim/src/phar.rs`:';
+    }
+
+    public function check(string $rootDir, array $excludes): array
+    {
+        $errors = [];
+
+        foreach ($this->embeddedFiles($rootDir) as $path) {
+            $relative = Paths::relativeTo($rootDir, $path);
+            if (in_array($relative, $excludes, true)) {
+                continue;
+            }
+
+            foreach (file($path) as $idx => $raw) {
+                if (!str_contains($raw, self::TOKEN)) {
+                    continue;
+                }
+
+                $errors[] = "{$relative}:" . ($idx + 1) . ': ' . trim($raw);
+            }
+        }
+
+        return $errors;
+    }
+
+    /**
+     * The sources whose bytes reach the binary: Rust code, and the PHP files the Rust code
+     * embeds with `include_str!`.
+     *
+     * @return list<string>
+     */
+    private function embeddedFiles(string $rootDir): array
+    {
+        $paths = FileFinder::rustFiles($rootDir);
+
+        foreach (glob("{$rootDir}/crates/*/php", GLOB_ONLYDIR) ?: [] as $phpDir) {
+            $iterator = new \RecursiveIteratorIterator(
+                new \RecursiveDirectoryIterator($phpDir, \FilesystemIterator::SKIP_DOTS),
+            );
+            foreach ($iterator as $file) {
+                /** @var \SplFileInfo $file */
+                if ($file->isFile()) {
+                    $paths[] = $file->getPathname();
+                }
+            }
+        }
+
+        sort($paths);
+
+        return $paths;
+    }
+}