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, 3 insertions, 2 deletions

diff --git a/crates/shirabe/src/util/forgejo.rs b/crates/shirabe/src/util/forgejo.rs
index 34d44b7b..6c18e4f6 100644
--- a/crates/shirabe/src/util/forgejo.rs
+++ b/crates/shirabe/src/util/forgejo.rs
@@ -6,6 +6,7 @@ use crate::io::IOInterface;
 use crate::io::IOInterfaceImmutable;
 use crate::io::io_interface;
 use crate::util::HttpDownloader;
+use shirabe_php_shim::Catch as _;
 
 #[derive(Debug)]
 pub struct Forgejo {
@@ -121,8 +122,8 @@ impl Forgejo {
             Ok(_) => {}
             Err(e) => {
                 let code = e
-                    .downcast_ref::<crate::downloader::TransportException>()
-                    .map(|te| te.code)
+                    .catch::<crate::downloader::TransportException>()
+                    .map(|te| te.get_code())
                     .unwrap_or(0);
                 if [403, 401, 404].contains(&code) {
                     self.io.write_error3(