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, 6 insertions, 12 deletions

diff --git a/crates/shirabe/src/json/json_validation_exception.rs b/crates/shirabe/src/json/json_validation_exception.rs
index a63edda3..cb7370d2 100644
--- a/crates/shirabe/src/json/json_validation_exception.rs
+++ b/crates/shirabe/src/json/json_validation_exception.rs
@@ -11,7 +11,7 @@ pub struct JsonValidationException {
 impl JsonValidationException {
     pub fn new(message: String, errors: Vec<String>) -> Self {
         Self {
-            inner: Exception { message, code: 0 },
+            inner: Exception::new(message),
             errors,
         }
     }
@@ -19,16 +19,10 @@ impl JsonValidationException {
     pub fn get_errors(&self) -> &Vec<String> {
         &self.errors
     }
-
-    pub fn get_message(&self) -> &str {
-        &self.inner.message
-    }
-}
-
-impl std::fmt::Display for JsonValidationException {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{}", self.inner.message)
-    }
 }
 
-impl std::error::Error for JsonValidationException {}
+shirabe_php_shim::impl_php_exception!(
+    JsonValidationException,
+    inner,
+    r"Composer\Json\JsonValidationException"
+);