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, 8 insertions, 26 deletions

diff --git a/crates/shirabe/src/downloader/transport_exception.rs b/crates/shirabe/src/downloader/transport_exception.rs
index 155a5ce4..da8b4c50 100644
--- a/crates/shirabe/src/downloader/transport_exception.rs
+++ b/crates/shirabe/src/downloader/transport_exception.rs
@@ -1,11 +1,10 @@
 //! ref: composer/src/Composer/Downloader/TransportException.php
 
-use shirabe_php_shim::PhpMixed;
+use shirabe_php_shim::{PhpMixed, RuntimeException};
 
 #[derive(Debug, Clone)]
 pub struct TransportException {
-    pub message: String,
-    pub code: i64,
+    inner: RuntimeException,
     pub(crate) headers: Option<Vec<String>>,
     pub(crate) response: Option<String>,
     pub(crate) status_code: Option<i64>,
@@ -15,8 +14,7 @@ pub struct TransportException {
 impl TransportException {
     pub fn new(message: String, code: i64) -> Self {
         Self {
-            message,
-            code,
+            inner: RuntimeException::with_code(message, code),
             headers: None,
             response: None,
             status_code: None,
@@ -24,20 +22,6 @@ impl TransportException {
         }
     }
 
-    /// PHP exposes ($message, $code = 0) — alias of `new` used at call sites where the
-    /// status/exception code is provided up-front.
-    pub fn new_with_code(message: String, code: i64) -> Self {
-        Self::new(message, code)
-    }
-
-    pub fn get_code(&self) -> i64 {
-        self.code
-    }
-
-    pub fn get_message(&self) -> &str {
-        &self.message
-    }
-
     pub fn set_headers(&mut self, headers: Vec<String>) {
         self.headers = Some(headers);
     }
@@ -71,10 +55,8 @@ impl TransportException {
     }
 }
 
-impl std::fmt::Display for TransportException {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{}", self.message)
-    }
-}
-
-impl std::error::Error for TransportException {}
+shirabe_php_shim::impl_php_exception!(
+    TransportException,
+    inner,
+    r"Composer\Downloader\TransportException"
+);