Respect --find-links in lock and sync (#4183)

## Summary

We already respect this command-line argument, I just forgot to wire it
up to the resolver.

crates/uv/src/commands/project/lock.rs

@@ -3,7 +3,7 @@ use anstream::eprint;
 use distribution_types::{IndexLocations, UnresolvedRequirementSpecification};
 use install_wheel_rs::linker::LinkMode;
 use uv_cache::Cache;
-use uv_client::RegistryClientBuilder;
+use uv_client::{FlatIndexClient, RegistryClientBuilder};
 use uv_configuration::{
     Concurrency, ConfigSettings, ExtrasSpecification, NoBinary, NoBuild, PreviewMode, Reinstall,
     SetupPyStrategy, Upgrade,
@@ -155,7 +155,6 @@ pub(super) async fn do_lock(
     let concurrency = Concurrency::default();
     let config_settings = ConfigSettings::default();
     let extras = ExtrasSpecification::default();
-    let flat_index = FlatIndex::default();
     let in_flight = InFlight::default();
     let index = InMemoryIndex::default();
     let link_mode = LinkMode::default();
@@ -167,6 +166,13 @@ pub(super) async fn do_lock(
     let hasher = HashStrategy::Generate;
     let options = OptionsBuilder::new().exclude_newer(exclude_newer).build();
 
+    // Resolve the flat indexes from `--find-links`.
+    let flat_index = {
+        let client = FlatIndexClient::new(&client, cache);
+        let entries = client.fetch(index_locations.flat_index()).await?;
+        FlatIndex::from_entries(entries, tags, &hasher, &no_build, &no_binary)
+    };
+
     // If an existing lockfile exists, build up a set of preferences.
     let LockedRequirements { preferences, git } = read_lockfile(workspace, &upgrade).await?;
 

crates/uv/src/commands/project/mod.rs

@@ -45,6 +45,9 @@ pub(crate) enum ProjectError {
     #[error(transparent)]
     Tags(#[from] platform_tags::TagsError),
 
+    #[error(transparent)]
+    FlatIndex(#[from] uv_client::FlatIndexError),
+
     #[error(transparent)]
     Lock(#[from] uv_resolver::LockError),
 

crates/uv/src/commands/project/sync.rs

@@ -3,7 +3,7 @@ use anyhow::Result;
 use distribution_types::IndexLocations;
 use install_wheel_rs::linker::LinkMode;
 use uv_cache::Cache;
-use uv_client::RegistryClientBuilder;
+use uv_client::{FlatIndexClient, RegistryClientBuilder};
 use uv_configuration::{
     Concurrency, ConfigSettings, ExtrasSpecification, NoBinary, NoBuild, PreviewMode, Reinstall,
     SetupPyStrategy,
@@ -116,7 +116,6 @@ pub(super) async fn do_sync(
     let concurrency = Concurrency::default();
     let config_settings = ConfigSettings::default();
     let dry_run = false;
-    let flat_index = FlatIndex::default();
     let git = GitResolver::default();
     let hasher = HashStrategy::default();
     let in_flight = InFlight::default();
@@ -127,6 +126,13 @@ pub(super) async fn do_sync(
     let reinstall = Reinstall::default();
     let setup_py = SetupPyStrategy::default();
 
+    // Resolve the flat indexes from `--find-links`.
+    let flat_index = {
+        let client = FlatIndexClient::new(&client, cache);
+        let entries = client.fetch(index_locations.flat_index()).await?;
+        FlatIndex::from_entries(entries, tags, &hasher, &no_build, &no_binary)
+    };
+
     // Create a build dispatch.
     let build_dispatch = BuildDispatch::new(
         &client,