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>

4 files changed, 22 insertions, 22 deletions

diff --git a/crates/shirabe/src/package/archiver/archivable_files_finder.rs b/crates/shirabe/src/package/archiver/archivable_files_finder.rs
index ad2b41ab..f60c57f1 100644
--- a/crates/shirabe/src/package/archiver/archivable_files_finder.rs
+++ b/crates/shirabe/src/package/archiver/archivable_files_finder.rs
@@ -28,10 +28,10 @@ impl ArchivableFilesFinder {
 
         let sources_real_path = realpath(sources);
         if sources_real_path.is_none() {
-            return Err(RuntimeException {
-                message: format!("Could not realpath() the source directory \"{}\"", sources),
-                code: 0,
-            }
+            return Err(RuntimeException::new(format!(
+                "Could not realpath() the source directory \"{}\"",
+                sources
+            ))
             .into());
         }
         let sources = fs.normalize_path(&sources_real_path.unwrap());
diff --git a/crates/shirabe/src/package/archiver/archive_manager.rs b/crates/shirabe/src/package/archiver/archive_manager.rs
index afc89f32..435843a6 100644
--- a/crates/shirabe/src/package/archiver/archive_manager.rs
+++ b/crates/shirabe/src/package/archiver/archive_manager.rs
@@ -114,10 +114,9 @@ impl ArchiveManager {
         ignore_filters: bool,
     ) -> anyhow::Result<String> {
         if format.is_empty() {
-            return Err(anyhow::anyhow!(InvalidArgumentException {
-                message: "Format must be specified".to_string(),
-                code: 0,
-            }));
+            return Err(
+                InvalidArgumentException::new("Format must be specified".to_string()).into(),
+            );
         }
 
         let mut usable_archiver_idx: Option<usize> = None;
@@ -131,10 +130,11 @@ impl ArchiveManager {
         let usable_archiver_idx = match usable_archiver_idx {
             Some(i) => i,
             None => {
-                return Err(anyhow::anyhow!(RuntimeException {
-                    message: format!("No archiver found to support {} format", format),
-                    code: 0,
-                }));
+                return Err(RuntimeException::new(format!(
+                    "No archiver found to support {} format",
+                    format
+                ))
+                .into());
             }
         };
 
diff --git a/crates/shirabe/src/package/archiver/phar_archiver.rs b/crates/shirabe/src/package/archiver/phar_archiver.rs
index fbab8c67..0968f2a4 100644
--- a/crates/shirabe/src/package/archiver/phar_archiver.rs
+++ b/crates/shirabe/src/package/archiver/phar_archiver.rs
@@ -101,10 +101,10 @@ impl ArchiverInterface for PharArchiver {
                 } else if format == "tar.gz" || format == "tar.bz2" {
                     let compress_algo = *compress_formats.get(format.as_str()).unwrap();
                     if !PharData::can_compress(compress_algo) {
-                        return Err(RuntimeException {
-                            message: format!("Can not compress to {} format", format),
-                            code: 0,
-                        }
+                        return Err(RuntimeException::new(format!(
+                            "Can not compress to {} format",
+                            format
+                        ))
                         .into());
                     }
                     if format == "tar.gz" && function_exists("gzcompress") {
@@ -124,10 +124,10 @@ impl ArchiverInterface for PharArchiver {
             if compress_formats.contains_key(format.as_str()) {
                 let compress_algo = *compress_formats.get(format.as_str()).unwrap();
                 if !PharData::can_compress(compress_algo) {
-                    return Err(RuntimeException {
-                        message: format!("Can not compress to {} format", format),
-                        code: 0,
-                    }
+                    return Err(RuntimeException::new(format!(
+                        "Can not compress to {} format",
+                        format
+                    ))
                     .into());
                 }
 
@@ -147,7 +147,7 @@ impl ArchiverInterface for PharArchiver {
                 "Could not create archive '{}' from '{}': {}",
                 target_outer, sources, e
             );
-            anyhow::anyhow!(RuntimeException { message, code: 0 })
+            RuntimeException::new(message).into()
         })
     }
 
diff --git a/crates/shirabe/src/package/archiver/zip_archiver.rs b/crates/shirabe/src/package/archiver/zip_archiver.rs
index 186d76c7..e5bb613d 100644
--- a/crates/shirabe/src/package/archiver/zip_archiver.rs
+++ b/crates/shirabe/src/package/archiver/zip_archiver.rs
@@ -111,7 +111,7 @@ impl ArchiverInterface for ZipArchiver {
             sources,
             zip.get_status_string()
         );
-        Err(RuntimeException { message, code: 0 }.into())
+        Err(RuntimeException::new(message).into())
     }
 
     fn supports(&self, format: String, _source_type: Option<String>) -> bool {