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, 10 insertions, 17 deletions

diff --git a/crates/shirabe/src/command/update_command.rs b/crates/shirabe/src/command/update_command.rs
index c928552a..02f32526 100644
--- a/crates/shirabe/src/command/update_command.rs
+++ b/crates/shirabe/src/command/update_command.rs
@@ -72,10 +72,9 @@ impl UpdateCommand {
         packages: Vec<String>,
     ) -> anyhow::Result<Vec<String>> {
         if !input.borrow().is_interactive() {
-            return Err(InvalidArgumentException {
-                message: "--interactive cannot be used in non-interactive terminals.".to_string(),
-                code: 0,
-            }
+            return Err(InvalidArgumentException::new(
+                "--interactive cannot be used in non-interactive terminals.".to_string(),
+            )
             .into());
         }
 
@@ -165,10 +164,9 @@ impl UpdateCommand {
         }
 
         if autocompleter_values.is_empty() {
-            return Err(RuntimeException {
-                message: "Could not find any package with new versions available".to_string(),
-                code: 0,
-            }
+            return Err(RuntimeException::new(
+                "Could not find any package with new versions available".to_string(),
+            )
             .into());
         }
 
@@ -210,11 +208,7 @@ impl UpdateCommand {
             return Ok(packages);
         }
 
-        Err(RuntimeException {
-            message: "Installation aborted.".to_string(),
-            code: 0,
-        }
-        .into())
+        Err(RuntimeException::new("Installation aborted.".to_string()).into())
     }
 
     fn create_version_selector(
@@ -450,10 +444,9 @@ impl Command for UpdateCommand {
             .unwrap_or(false)
         {
             if !composer.get_locker().borrow_mut().is_locked() {
-                return Err(InvalidArgumentException {
-                    message: "patch-only can only be used with a lock file present".to_string(),
-                    code: 0,
-                }
+                return Err(InvalidArgumentException::new(
+                    "patch-only can only be used with a lock file present".to_string(),
+                )
                 .into());
             }
             for package in composer