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, 11 insertions, 15 deletions

diff --git a/crates/shirabe/src/repository/artifact_repository.rs b/crates/shirabe/src/repository/artifact_repository.rs
index 99f340d1..2d16f137 100644
--- a/crates/shirabe/src/repository/artifact_repository.rs
+++ b/crates/shirabe/src/repository/artifact_repository.rs
@@ -47,10 +47,9 @@ impl ArtifactRepository {
         io: std::rc::Rc<std::cell::RefCell<dyn IOInterface>>,
     ) -> anyhow::Result<Self> {
         if !extension_loaded("zip") {
-            return Err(RuntimeException {
-                message: "The artifact repository requires PHP's zip extension".to_string(),
-                code: 0,
-            }
+            return Err(RuntimeException::new(
+                "The artifact repository requires PHP's zip extension".to_string(),
+            )
             .into());
         }
 
@@ -171,13 +170,10 @@ impl ArtifactRepository {
         } else if file_extension == "zip" {
             file_type = "zip";
         } else {
-            return Err(RuntimeException {
-                message: format!(
-                    "Files with \"{}\" extensions aren't supported. Only ZIP and TAR/TAR.GZ/TGZ archives are supported.",
-                    file_extension
-                ),
-                code: 0,
-            }
+            return Err(RuntimeException::new(format!(
+                "Files with \"{}\" extensions aren't supported. Only ZIP and TAR/TAR.GZ/TGZ archives are supported.",
+                file_extension
+            ))
             .into());
         }
 
@@ -228,10 +224,10 @@ impl ArtifactRepository {
             .unwrap_or_default();
         match self.loader.load(cfg, None) {
             Ok(package) => Ok(Some(package)),
-            Err(exception) => Err(UnexpectedValueException {
-                message: format!("Failed loading package in {}: {}", pathname, exception),
-                code: 0,
-            }
+            Err(exception) => Err(UnexpectedValueException::new(format!(
+                "Failed loading package in {}: {}",
+                pathname, exception
+            ))
             .into()),
         }
     }