feat: support uv.lock as version-file (#379)

Adds `uv.lock` as a supported `version-file` format, alongside the
existing
`pyproject.toml` and `requirements.txt`. A `uv.lock` pins the exact
resolved
ruff version, so reading it gives a reproducible install that matches
the
project's lockfile — the single source of truth — instead of the
lower-bound /
range typically declared in `pyproject.toml`.

The parser reads the `[[package]]` entry whose `name` is `ruff` and
returns its
`version`. If ruff is absent or the file cannot be parsed, the action
warns and
falls back to `latest` (same behaviour as the other formats).

Validation:
- `npm run all` — tsc typecheck clean, biome clean, dist rebuilt, jest
65/65 pass
- Added unit tests (`__tests__/version/file-parser.test.ts`) + a
`uv.lock` fixture
- Added an integration job (`test-default-version-from-uv-lock`) that
runs the
  action against the fixture and asserts ruff 0.9.5 is installed

closes #375

dist/ruff-action/index.cjs

@@ -31702,6 +31702,14 @@ var VERSION_FILE_PARSERS = [
     },
     supports: (filePath) => filePath.endsWith("pyproject.toml")
   },
+  {
+    format: "uv.lock",
+    parse: (filePath) => {
+      const fileContent = import_node_fs2.default.readFileSync(filePath, "utf-8");
+      return getRuffVersionFromUvLockContent(fileContent);
+    },
+    supports: (filePath) => filePath.endsWith("uv.lock")
+  },
   {
     format: "requirements",
     parse: (filePath) => {
@@ -31775,6 +31783,15 @@ function getRuffVersionFromPyprojectContent(pyprojectContent) {
 function parsePyprojectContent(pyprojectContent) {
   return parse2(pyprojectContent);
 }
+function getRuffVersionFromUvLockContent(uvLockContent) {
+  const uvLock = parse(uvLockContent);
+  const ruffPackage = (uvLock.package || []).find((pkg) => pkg.name === "ruff");
+  if (ruffPackage?.version === void 0) {
+    return void 0;
+  }
+  info(`Found ruff version in uv.lock: ${ruffPackage.version}`);
+  return ruffPackage.version;
+}
 function getVersionFileParser(filePath) {
   return VERSION_FILE_PARSERS.find((parser) => parser.supports(filePath));
 }