test: port Composer tests unblocked by mockall, add seams

Port 11 categories of previously-ignored Composer tests now reachable with
the mockall crate: DownloadManager, VCS/Perforce/File downloaders,
VersionSelector, PlatformRepository, Auditor, installer/FilesystemRepository,
RootPackageLoader, util auth/http, commands, and Cache.

Extract test seams additively on concrete structs as *Interface traits
(Runtime, HhvmDetector, VersionGuesser, RepositorySet, Perforce,
BinaryInstaller) plus mock-field seams (Cache, Filesystem); consumers take
trait objects. Mocks are defined locally in the test crates via
mockall::mock!, since automock-generated mocks are cfg(test)-gated and
invisible across the integration-test boundary.

dataProviders are ported in full; tests blocked by unported shims stay
#[ignore] with documented reasons rather than reduced or weakened.

Fix product bugs surfaced by the ports:
- util/github: use the exception code, not the HTTP status, for 401/403
- advisory: serialize empty audit maps as [] to match PHP json_encode
- repository/filesystem and downloader/file: fix RefCell double-borrow panics

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/crates/shirabe/tests/platform/hhvm_detector_test.rs b/crates/shirabe/tests/platform/hhvm_detector_test.rs
index 71da314..f1ec656 100644
--- a/crates/shirabe/tests/platform/hhvm_detector_test.rs
+++ b/crates/shirabe/tests/platform/hhvm_detector_test.rs
@@ -1,6 +1,7 @@
 //! ref: composer/tests/Composer/Test/Platform/HhvmDetectorTest.php
 
 use shirabe::platform::hhvm_detector::HhvmDetector;
+use shirabe::platform::hhvm_detector::HhvmDetectorInterface;
 use shirabe::util::Platform;
 use shirabe::util::ProcessExecutor;
 use shirabe_external_packages::symfony::process::ExecutableFinder;