fix(install): limit preparer concurrency to prevent file handle exhaustion

crates/uv-bench/benches/uv.rs

@@ -256,6 +256,7 @@ mod resolver {
                 client,
                 &build_context,
                 concurrency.downloads_semaphore.clone(),
+                concurrency.source_distribution_semaphore.clone(),
             ),
         )?;
 

crates/uv-configuration/src/concurrency.rs

@@ -24,6 +24,8 @@ pub struct Concurrency {
     pub downloads_semaphore: Arc<Semaphore>,
     /// A global semaphore to limit the number of concurrent builds.
     pub builds_semaphore: Arc<Semaphore>,
+    /// A global semaphore to limit the number of concurrent source distribution preparations.
+    pub source_distribution_semaphore: Arc<Semaphore>,
 }
 
 /// Custom `Debug` to hide semaphore fields from `--show-settings` output.
@@ -56,6 +58,7 @@ impl Concurrency {
             installs,
             downloads_semaphore: Arc::new(Semaphore::new(downloads)),
             builds_semaphore: Arc::new(Semaphore::new(builds)),
+            source_distribution_semaphore: Arc::new(Semaphore::new(builds)),
         }
     }
 

crates/uv-dispatch/src/lib.rs

@@ -268,6 +268,7 @@ impl BuildContext for BuildDispatch<'_> {
                 self.client,
                 self,
                 self.concurrency.downloads_semaphore.clone(),
+                self.concurrency.source_distribution_semaphore.clone(),
             )
             .with_build_stack(build_stack),
         )?;
@@ -361,6 +362,7 @@ impl BuildContext for BuildDispatch<'_> {
                     self.client,
                     self,
                     self.concurrency.downloads_semaphore.clone(),
+                    self.concurrency.source_distribution_semaphore.clone(),
                 )
                 .with_build_stack(build_stack),
             );

crates/uv-distribution/src/distribution_database.rs

@@ -63,10 +63,11 @@ impl<'a, Context: BuildContext> DistributionDatabase<'a, Context> {
         client: &'a RegistryClient,
         build_context: &'a Context,
         downloads_semaphore: Arc<Semaphore>,
+        source_distribution_semaphore: Arc<Semaphore>,
     ) -> Self {
         Self {
             build_context,
-            builder: SourceDistributionBuilder::new(build_context),
+            builder: SourceDistributionBuilder::new(build_context, source_distribution_semaphore),
             client: ManagedClient::new(client, downloads_semaphore),
             reporter: None,
         }