refactor(downloader): turn DownloadManager into downloader registry

Reshape DownloadManager from a hard-coded VCS match into a registry of
DownloaderInterface instances keyed by source type, mirroring
Composer's DownloadManager — with prefer-source/dist preferences, an
IO handle, and a files cache. ArchiveManager now resolves dist
sources through a shared DownloadManager instead of calling
download_dist directly, and Composer::require / try_load take an IO
so it flows through the factory wiring.

1 files changed, 13 insertions, 4 deletions

diff --git a/crates/mozart-core/src/downloader/hg_downloader.rs b/crates/mozart-core/src/downloader/hg_downloader.rs
index 9fb918e..dfe3546 100644
--- a/crates/mozart-core/src/downloader/hg_downloader.rs
+++ b/crates/mozart-core/src/downloader/hg_downloader.rs
@@ -1,16 +1,19 @@
+use crate::downloader::{DownloaderInterface, VcsDownloader};
+use crate::vcs::process::ProcessExecutor;
+use crate::vcs::util::hg::HgUtil;
 use anyhow::Result;
 use std::path::Path;
 
-use crate::{downloader::VcsDownloader, vcs::util::hg::HgUtil};
-
 /// Mercurial downloader using clone/pull/update.
 pub struct HgDownloader {
     hg_util: HgUtil,
 }
 
 impl HgDownloader {
-    pub fn new(hg_util: HgUtil) -> Self {
-        Self { hg_util }
+    pub fn new(process: ProcessExecutor) -> Self {
+        Self {
+            hg_util: HgUtil::new(process),
+        }
     }
 }
 
@@ -82,3 +85,9 @@ impl VcsDownloader for HgDownloader {
         false
     }
 }
+
+impl DownloaderInterface for HgDownloader {
+    fn as_vcs_downloader(&self) -> Option<&dyn VcsDownloader> {
+        Some(self)
+    }
+}