feat: add pr view and checks (task 0009)

Add `pr view <n>` and `pr checks <n>`, built on the truncation machinery
and review fetches from earlier slices.

`pr view` uses the three-call fetch pattern (PR + reviews in parallel, then
the head commit's combined status) so `checks`, `comment_count`, and
`review_count` are in the default output; `--comments`, `--reviews`, and
`--full` behave as on `issue view`, with `--reviews` exposing Gitea's
`official`/`stale` fields plus per-review inline comments.

`pr checks <n>` renders the checks summary line and the `{ name, conclusion }`
rows, or the scalar no-CI message when no statuses exist.

The state→conclusion mapping and summary live in a new `src/checks.ts`;
`commentRows` is extracted into `src/comment.ts` and shared with `issue view`.

test/checks.test.ts

@@ -0,0 +1,37 @@
+import { describe, expect, it } from "vitest";
+import type { CommitStatus } from "gitea-js";
+import { summarizeChecks } from "../src/checks.js";
+
+describe("summarizeChecks", () => {
+  it("maps success commit statuses to pass checks and omits zero skipped/pending segments", () => {
+    const statuses = [
+      { context: "build", status: "success" },
+      { context: "test", status: "success" },
+    ] as CommitStatus[];
+
+    const result = summarizeChecks(statuses);
+
+    expect(result.checks).toEqual([
+      { name: "build", conclusion: "pass" },
+      { name: "test", conclusion: "pass" },
+    ]);
+    expect(result.summary).toBe("2 passed, 0 failed, 2 total");
+  });
+
+  it("maps failure, error, and warning states all to fail (warning counts as failure)", () => {
+    const statuses = [
+      { context: "a", status: "failure" },
+      { context: "b", status: "error" },
+      { context: "c", status: "warning" },
+    ] as CommitStatus[];
+
+    const result = summarizeChecks(statuses);
+
+    expect(result.checks).toEqual([
+      { name: "a", conclusion: "fail" },
+      { name: "b", conclusion: "fail" },
+      { name: "c", conclusion: "fail" },
+    ]);
+    expect(result.summary).toBe("0 passed, 3 failed, 3 total");
+  });
+});