feat: scaffold CLI with fetch and render-md subcommands

tests/cli_parse_tests.rs

@@ -0,0 +1,34 @@
+use clap::Parser;
+use gitea_pr_review::cli::{Cli, Commands, OutputFormat};
+
+#[test]
+fn parse_fetch_default_format() {
+    let cli = Cli::try_parse_from(["gitea-pr-review", "fetch", "12"]).unwrap();
+    match cli.command {
+        Commands::Fetch(args) => {
+            assert_eq!(args.pr_index, 12);
+            assert_eq!(args.format, OutputFormat::Markdown);
+            assert!(args.out.is_none());
+        }
+        _ => panic!("expected fetch"),
+    }
+}
+
+#[test]
+fn parse_render_md_requires_input() {
+    let cli = Cli::try_parse_from([
+        "gitea-pr-review",
+        "render-md",
+        "--in",
+        "sample.json",
+    ])
+    .unwrap();
+
+    match cli.command {
+        Commands::RenderMd(args) => {
+            assert_eq!(args.input.display().to_string(), "sample.json");
+            assert!(args.out.is_none());
+        }
+        _ => panic!("expected render-md"),
+    }
+}