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, 1 deletions

diff --git a/crates/shirabe/src/util/github.rs b/crates/shirabe/src/util/github.rs
index 01a5dd1f..066f0ff5 100644
--- a/crates/shirabe/src/util/github.rs
+++ b/crates/shirabe/src/util/github.rs
@@ -9,6 +9,7 @@ use crate::util::HttpDownloader;
 use crate::util::ProcessExecutor;
 use indexmap::IndexMap;
 use shirabe_external_packages::composer::pcre::{CaptureKey, Preg};
+use shirabe_php_shim::Catch as _;
 use shirabe_php_shim::{PhpMixed, date, in_array_loose, php_regex, stripos, strtolower};
 
 #[derive(Debug)]
@@ -233,7 +234,7 @@ impl GitHub {
             Ok(_) => {}
             Err(te) => {
                 let code = te
-                    .downcast_ref::<crate::downloader::TransportException>()
+                    .catch::<crate::downloader::TransportException>()
                     .map(|t| t.get_code())
                     .unwrap_or(0);
                 if code == 403 || code == 401 {