feat(vcs): wire cache-vcs-dir setting through to drivers

DriverConfig used to expose a generic cache_dir hardcoded to a
relative ".cache/mozart/vcs", with each driver appending its own
"git"/"hg" subdir. As a result, the cache-vcs-dir setting (and
COMPOSER_CACHE_VCS_DIR env var) had no effect on where mirrors
were actually stored.

Replace cache_dir with cache_vcs_dir, resolving its default the
same way Composer does (COMPOSER_CACHE_VCS_DIR → COMPOSER_CACHE_DIR/vcs
→ XDG/HOME fallbacks), and have GitDriver/HgDriver use it directly.
This brings the Mozart cache layout in line with Composer's: a single
shared vcs root with one subdirectory per sanitized URL.

1 files changed, 2 insertions, 2 deletions

diff --git a/crates/mozart-vcs/tests/git_driver_test.rs b/crates/mozart-vcs/tests/git_driver_test.rs
index a8f0ce7..04b224b 100644
--- a/crates/mozart-vcs/tests/git_driver_test.rs
+++ b/crates/mozart-vcs/tests/git_driver_test.rs
@@ -77,7 +77,7 @@ async fn test_git_driver_local_repo() {
     create_test_repo(repo_dir.path());
 
     let config = DriverConfig {
-        cache_dir: cache_dir.path().to_path_buf(),
+        cache_vcs_dir: cache_dir.path().to_path_buf(),
         ..DriverConfig::default()
     };
 
@@ -237,7 +237,7 @@ async fn test_vcs_repository_scan() {
     create_test_repo(repo_dir.path());
 
     let config = DriverConfig {
-        cache_dir: cache_dir.path().to_path_buf(),
+        cache_vcs_dir: cache_dir.path().to_path_buf(),
         ..DriverConfig::default()
     };