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, 2 insertions, 4 deletions

diff --git a/crates/shirabe/tests/package/archiver/archive_manager_test.rs b/crates/shirabe/tests/package/archiver/archive_manager_test.rs
index a7235bf9..84feb5bc 100644
--- a/crates/shirabe/tests/package/archiver/archive_manager_test.rs
+++ b/crates/shirabe/tests/package/archiver/archive_manager_test.rs
@@ -13,6 +13,7 @@ use shirabe::util::ProcessExecutor;
 use shirabe::util::http_downloader::HttpDownloader;
 use shirabe::util::r#loop::Loop;
 use shirabe_external_packages::symfony::process::Process;
+use shirabe_php_shim::Catch as _;
 use shirabe_php_shim::{
     PhpMixed, file_exists, file_put_contents, realpath, sys_get_temp_dir, unlink,
 };
@@ -159,10 +160,7 @@ fn test_unknown_format() {
     );
 
     let err = result.expect_err("expected RuntimeException for unknown format");
-    assert!(
-        err.downcast_ref::<shirabe_php_shim::RuntimeException>()
-            .is_some()
-    );
+    assert!(err.is_instanceof::<shirabe_php_shim::RuntimeException>());
 }
 
 // ref: ArchiveManagerTest::testArchiveTar / testArchiveCustomFileName.