feat: enforce output version v1 and add version subcommand

tests/e2e_smoke_tests.rs

@@ -8,6 +8,7 @@ fn render_md_reads_json_and_outputs_markdown_to_stdout() {
     std::fs::write(
         input.path(),
         r#"{
+  "version": "v1",
   "meta": {
     "repo": "org/repo",
     "pr_index": 1,
@@ -52,6 +53,7 @@ fn render_md_writes_to_out_file_when_requested() {
     std::fs::write(
         input.path(),
         r#"{
+  "version": "v1",
   "meta": {
     "repo": "org/repo",
     "pr_index": 2,
@@ -291,6 +293,59 @@ fn fetch_writes_json_to_out_file_when_requested() {
     let written = std::fs::read_to_string(output.path()).unwrap();
     assert!(written.contains("\"repo\": \"org/repo\""));
     assert!(written.contains("\"pr_index\": 8"));
+    assert!(written.contains("\"version\": \"v1\""));
     assert!(written.contains("\"fetched_at\":"));
     assert!(written.contains("\"head_branch\": \"feature/y\""));
 }
+
+#[test]
+fn render_md_fails_when_version_mismatch() {
+    let input = NamedTempFile::new().unwrap();
+    std::fs::write(
+        input.path(),
+        r#"{
+  "version": "v2",
+  "meta": {
+    "repo": "org/repo",
+    "pr_index": 3,
+    "title": "t3",
+    "description": "PR body",
+    "fetched_at": "2026-04-08T12:34:56Z",
+    "state": "open",
+    "author": "a",
+    "base_branch": "main",
+    "head_branch": "f",
+    "created_at": "2026-04-08T10:00:00Z",
+    "updated_at": "2026-04-08T11:00:00Z",
+    "merged_at": null
+  },
+  "commits": [],
+  "diff_stat": {
+    "files_changed": 0,
+    "additions": 0,
+    "deletions": 0,
+    "files": []
+  },
+  "reviews": [],
+  "threads": []
+}"#,
+    )
+    .unwrap();
+
+    Command::cargo_bin("gitea-pr-review")
+        .unwrap()
+        .args(["render-md", "--in", input.path().to_str().unwrap()])
+        .assert()
+        .failure();
+}
+
+#[test]
+fn version_subcommand_prints_current_version() {
+    let assert = Command::cargo_bin("gitea-pr-review")
+        .unwrap()
+        .arg("version")
+        .assert()
+        .success();
+    let stdout = String::from_utf8(assert.get_output().stdout.clone()).unwrap();
+    assert_eq!(stdout.trim(), "v1");
+}