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, 8 deletions

diff --git a/crates/shirabe/src/installer/metapackage_installer.rs b/crates/shirabe/src/installer/metapackage_installer.rs
index 52c152ea..99d3786c 100644
--- a/crates/shirabe/src/installer/metapackage_installer.rs
+++ b/crates/shirabe/src/installer/metapackage_installer.rs
@@ -86,10 +86,10 @@ impl InstallerInterface for MetapackageInstaller {
         target: PackageInterfaceHandle,
     ) -> anyhow::Result<Option<PhpMixed>> {
         if !repo.borrow_mut().has_package(initial.clone())? {
-            return Err(InvalidArgumentException {
-                message: format!("Package is not installed: {}", initial),
-                code: 0,
-            }
+            return Err(InvalidArgumentException::new(format!(
+                "Package is not installed: {}",
+                initial
+            ))
             .into());
         }
 
@@ -115,10 +115,10 @@ impl InstallerInterface for MetapackageInstaller {
         package: PackageInterfaceHandle,
     ) -> anyhow::Result<Option<PhpMixed>> {
         if !repo.borrow_mut().has_package(package.clone())? {
-            return Err(InvalidArgumentException {
-                message: format!("Package is not installed: {}", package),
-                code: 0,
-            }
+            return Err(InvalidArgumentException::new(format!(
+                "Package is not installed: {}",
+                package
+            ))
             .into());
         }