feat: support uv.lock as a version-file source (#918)

Adds `uv.lock` as a supported `version-file` source. When `uv` is locked
as a
dependency in `uv.lock`, the action now installs the exact pinned
version,
closing the gap reported in #682.

This is useful for deterministic CI: the same uv version is used until
the
lockfile is updated, which avoids "CI worked yesterday, fails today"
drift and
reduces supply-chain exposure from auto-installing the latest release.

The implementation mirrors the existing `version-file` parsers — a new
`uv.lock`
entry in the parser registry reads the `[[package]]` whose `name = "uv"`
and
returns its locked `version`. Scoped to explicit `version-file:
uv.lock`;
workspace auto-detection is left as a possible follow-up to avoid
precedence
ambiguity with `uv.toml` / `pyproject.toml`.

Validation (local, Node 23; dist build is esbuild-deterministic):
- `npm run all` → build clean, biome clean, package clean, jest 77/77
- New tests: 3 unit (`uv-lock-file.test.ts`) + 1 integration — exact pin
resolves
  through the full pipeline (`uv.lock` → `0.8.17`)
- dist rebuilt + committed (single bundle, no spurious churn)

related: #682

__tests__/version/version-request-resolver.test.ts

@@ -63,6 +63,24 @@ describe("resolveVersionRequest", () => {
     });
   });
 
+  it("uses the exact uv version locked in uv.lock when it is passed via version-file", () => {
+    const workingDirectory = createTempProject({
+      "uv.lock": `version = 1\n\n[[package]]\nname = "uv"\nversion = "0.8.17"\nsource = { registry = "https://pypi.org/simple" }\n`,
+    });
+
+    const request = resolveVersionRequest({
+      versionFile: path.join(workingDirectory, "uv.lock"),
+      workingDirectory,
+    });
+
+    expect(request).toEqual({
+      format: "uv.lock",
+      source: "version-file",
+      sourcePath: path.join(workingDirectory, "uv.lock"),
+      specifier: "0.8.17",
+    });
+  });
+
   it("uses requirements.txt when it is passed via version-file", () => {
     const workingDirectory = createTempProject({
       "requirements.txt": "uv==0.6.17\nuvicorn==0.35.0\n",