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, 5 deletions

diff --git a/crates/mozart-core/src/downloader/svn_downloader.rs b/crates/mozart-core/src/downloader/svn_downloader.rs
index c78f9b7..690a090 100644
--- a/crates/mozart-core/src/downloader/svn_downloader.rs
+++ b/crates/mozart-core/src/downloader/svn_downloader.rs
@@ -1,11 +1,11 @@
+use crate::downloader::{DownloaderInterface, VcsDownloader};
+use crate::vcs::process::ProcessExecutor;
+use crate::vcs::util::svn::SvnUtil;
 use anyhow::Result;
 use regex::Regex;
 use std::path::Path;
 use std::sync::LazyLock;
 
-use crate::downloader::VcsDownloader;
-use crate::vcs::util::svn::SvnUtil;
-
 /// Match any non-`X` status line (mirror of Composer's
 /// `{^ *[^X ] +}m`). Ignores externals (`X` prefix).
 static SVN_STATUS_RE: LazyLock<Regex> = LazyLock::new(|| Regex::new(r"(?m)^ *[^X ] +").unwrap());
@@ -16,8 +16,10 @@ pub struct SvnDownloader {
 }
 
 impl SvnDownloader {
-    pub fn new(svn_util: SvnUtil) -> Self {
-        Self { svn_util }
+    pub fn new(process: ProcessExecutor) -> Self {
+        Self {
+            svn_util: SvnUtil::new(process),
+        }
     }
 }
 
@@ -83,3 +85,9 @@ impl VcsDownloader for SvnDownloader {
         false
     }
 }
+
+impl DownloaderInterface for SvnDownloader {
+    fn as_vcs_downloader(&self) -> Option<&dyn VcsDownloader> {
+        Some(self)
+    }
+}