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, 14 insertions, 20 deletions

diff --git a/crates/shirabe/src/util/http/proxy_item.rs b/crates/shirabe/src/util/http/proxy_item.rs
index 1a0b3ee8..73948f88 100644
--- a/crates/shirabe/src/util/http/proxy_item.rs
+++ b/crates/shirabe/src/util/http/proxy_item.rs
@@ -20,28 +20,22 @@ impl ProxyItem {
         let syntax_error = format!("unsupported `{}` syntax", env_name);
 
         if strpbrk(&proxy_url, "\r\n\t").is_some() {
-            return Err(RuntimeException {
-                message: syntax_error,
-                code: 0,
-            });
+            return Err(RuntimeException::new(syntax_error));
         }
 
         let proxy_parsed = parse_url_all(&proxy_url);
         let proxy = match proxy_parsed.as_array() {
             None => {
-                return Err(RuntimeException {
-                    message: syntax_error,
-                    code: 0,
-                });
+                return Err(RuntimeException::new(syntax_error));
             }
             Some(a) => a.clone(),
         };
 
         if !proxy.contains_key("host") {
-            return Err(RuntimeException {
-                message: format!("unable to find proxy host in {}", env_name),
-                code: 0,
-            });
+            return Err(RuntimeException::new(format!(
+                "unable to find proxy host in {}",
+                env_name
+            )));
         }
 
         let scheme = if proxy.contains_key("scheme") {
@@ -100,16 +94,16 @@ impl ProxyItem {
         // but is considered valid depending on the PHP or Curl version.
         let port = match port {
             None => {
-                return Err(RuntimeException {
-                    message: format!("unable to find proxy port in {}", env_name),
-                    code: 0,
-                });
+                return Err(RuntimeException::new(format!(
+                    "unable to find proxy port in {}",
+                    env_name
+                )));
             }
             Some(0) => {
-                return Err(RuntimeException {
-                    message: format!("port 0 is reserved in {}", env_name),
-                    code: 0,
-                });
+                return Err(RuntimeException::new(format!(
+                    "port 0 is reserved in {}",
+                    env_name
+                )));
             }
             Some(p) => p,
         };