Respect cached local --find-links in install plan (#2907)

## Summary

I think this is kind of just an oversight. If a wheel is available via
`--find-links`, and the index is "local", we never find it in the cache.

## Test Plan

`cargo test`

crates/uv-distribution/src/distribution_database.rs

@@ -150,10 +150,9 @@ impl<'a, Context: BuildContext + Send + Sync> DistributionDatabase<'a, Context>
                         Url::parse(url).map_err(|err| Error::Url(url.clone(), err))?
                     }
                     FileLocation::Path(path) => {
-                        let url = Url::from_file_path(path).expect("path is absolute");
                         let cache_entry = self.build_context.cache().entry(
                             CacheBucket::Wheels,
-                            WheelCache::Url(&url).wheel_dir(wheel.name().as_ref()),
+                            WheelCache::Index(&wheel.index).wheel_dir(wheel.name().as_ref()),
                             wheel.filename.stem(),
                         );
                         return self

crates/uv-distribution/src/index/registry_wheel_index.rs

@@ -83,7 +83,10 @@ impl<'a> RegistryWheelIndex<'a> {
         let flat_index_urls: Vec<IndexUrl> = index_locations
             .flat_index()
             .filter_map(|flat_index| match flat_index {
-                FlatIndexLocation::Path(_) => None,
+                FlatIndexLocation::Path(path) => {
+                    let path = fs_err::canonicalize(path).ok()?;
+                    Some(IndexUrl::Url(VerbatimUrl::from_path(path)))
+                }
                 FlatIndexLocation::Url(url) => {
                     Some(IndexUrl::Url(VerbatimUrl::unknown(url.clone())))
                 }

crates/uv/tests/pip_sync.rs

@@ -2575,6 +2575,54 @@ fn find_links_offline_no_match() -> Result<()> {
     Ok(())
 }
 
+/// Sync using `--find-links` with a local directory. Ensure that cached wheels are reused.
+#[test]
+fn find_links_cache() -> Result<()> {
+    let context = TestContext::new("3.12");
+
+    let requirements_txt = context.temp_dir.child("requirements.txt");
+    requirements_txt.write_str(indoc! {r"
+        tqdm
+    "})?;
+
+    // Install `tqdm`.
+    uv_snapshot!(context.filters(), command(&context)
+        .arg("requirements.txt")
+        .arg("--find-links")
+        .arg(context.workspace_root.join("scripts/links/")), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Resolved 1 package in [TIME]
+    Downloaded 1 package in [TIME]
+    Installed 1 package in [TIME]
+     + tqdm==1000.0.0
+    "###
+    );
+
+    // Reinstall `tqdm` with `--reinstall`. Ensure that the wheel is reused.
+    uv_snapshot!(context.filters(), command(&context)
+        .arg("requirements.txt")
+        .arg("--reinstall")
+        .arg("--find-links")
+        .arg(context.workspace_root.join("scripts/links/")), @r###"
+    success: true
+    exit_code: 0
+    ----- stdout -----
+
+    ----- stderr -----
+    Uninstalled 1 package in [TIME]
+    Installed 1 package in [TIME]
+     - tqdm==1000.0.0
+     + tqdm==1000.0.0
+    "###
+    );
+
+    Ok(())
+}
+
 /// Install without network access via the `--offline` flag.
 #[test]
 fn offline() -> Result<()> {