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, 5 insertions, 4 deletions

diff --git a/crates/shirabe-class-map-generator/src/class_map.rs b/crates/shirabe-class-map-generator/src/class_map.rs
index 0b828be4..65eb3790 100644
--- a/crates/shirabe-class-map-generator/src/class_map.rs
+++ b/crates/shirabe-class-map-generator/src/class_map.rs
@@ -92,10 +92,11 @@ impl ClassMap {
     pub fn get_class_path(&self, class_name: &str) -> anyhow::Result<&str> {
         match self.map.get(class_name) {
             Some(path) => Ok(path.as_str()),
-            None => Err(anyhow::anyhow!(OutOfBoundsException {
-                message: format!("Class {} is not present in the map", class_name),
-                code: 0,
-            })),
+            None => Err(OutOfBoundsException::new(format!(
+                "Class {} is not present in the map",
+                class_name
+            ))
+            .into()),
         }
     }