feat(php-shim): give ported exceptions PHP's class hierarchy

Ported exceptions were flat structs reached with `downcast_ref`, so
Composer's `catch (\RuntimeException $e)` only matched the exact leaf
type and `get_class($e)` had nothing to report. Each exception now
embeds an instance of the class it extends and travels inside an
`AnyThrowable`; `Catch::catch`/`catch_mut` walk that chain, and
`PhpClass::php_class_name` yields the PHP FQCN.

Dropping the `std::error::Error` impls from the exception types leaves
`AnyThrowable` as the only route into an `anyhow::Error`, so the walk
cannot be bypassed. A `no_exception_downcast` linter catches the
`downcast::<X>()` calls that would now silently answer `None`.

Three sites change behavior as a result: the `TransportException`
exit-code override reaches `MaxFileSizeExceededException`, the
`catch (\LogicException)` in findSimilar() reaches its subclasses, and
rendered exception titles carry the real class name rather than a
guess. `get_class_err()` is no longer a `todo!()`, which re-enables
FilesystemRepositoryTest::testCorruptedRepositoryFile.

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

1 files changed, 10 insertions, 12 deletions

diff --git a/crates/shirabe-external-packages/src/symfony/filesystem/exception/io_exception.rs b/crates/shirabe-external-packages/src/symfony/filesystem/exception/io_exception.rs
index e666e9ea..ffe80ea1 100644
--- a/crates/shirabe-external-packages/src/symfony/filesystem/exception/io_exception.rs
+++ b/crates/shirabe-external-packages/src/symfony/filesystem/exception/io_exception.rs
@@ -1,9 +1,10 @@
 //! ref: composer/vendor/symfony/filesystem/Exception/IOException.php
 
+use shirabe_php_shim::RuntimeException;
+
 #[derive(Debug)]
 pub struct IOException {
-    pub message: String,
-    pub code: i64,
+    inner: RuntimeException,
     pub path: Option<String>,
 }
 
@@ -11,21 +12,18 @@ impl IOException {
     pub fn new(
         message: String,
         code: i64,
-        _previous: Option<Box<dyn std::error::Error + Send + Sync>>,
+        previous: Option<std::sync::Arc<shirabe_php_shim::AnyThrowable>>,
         path: Option<String>,
     ) -> Self {
         Self {
-            message,
-            code,
+            inner: RuntimeException::with_code_and_previous(message, code, previous),
             path,
         }
     }
 }
 
-impl std::fmt::Display for IOException {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{}", self.message)
-    }
-}
-
-impl std::error::Error for IOException {}
+shirabe_php_shim::impl_php_exception!(
+    IOException,
+    inner,
+    r"Symfony\Component\Filesystem\Exception\IOException"
+);