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, 4 deletions

diff --git a/crates/shirabe/src/command/search_command.rs b/crates/shirabe/src/command/search_command.rs
index 4bf75c8b..51432ed9 100644
--- a/crates/shirabe/src/command/search_command.rs
+++ b/crates/shirabe/src/command/search_command.rs
@@ -181,10 +181,9 @@ impl Command for SearchCommand {
                 .as_bool()
                 .unwrap_or(false)
             {
-                return Err(InvalidArgumentException {
-                    message: "--only-name and --only-vendor cannot be used together".to_string(),
-                    code: 0,
-                }
+                return Err(InvalidArgumentException::new(
+                    "--only-name and --only-vendor cannot be used together".to_string(),
+                )
                 .into());
             }
             mode = repository_interface::SEARCH_NAME;