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/pr-checks.test.ts

@@ -0,0 +1,126 @@
+import { afterEach, describe, expect, it } from "vitest";
+import { startFixtureServer, type FixtureServer } from "./fixture-server.js";
+import { runCliTest, testModeEnv } from "./harness.js";
+
+const PULL_PATH = "/api/v1/repos/testowner/testrepo/pulls/5";
+const STATUS_PATH = "/api/v1/repos/testowner/testrepo/commits/abc123/status";
+
+let server: FixtureServer;
+
+afterEach(async () => {
+  await server.close();
+});
+
+describe("pr checks", () => {
+  it("renders a summary line and a checks list mapping each commit-status state", async () => {
+    server = await startFixtureServer([
+      {
+        method: "GET",
+        path: PULL_PATH,
+        body: { number: 5, head: { sha: "abc123", ref: "feature" } },
+      },
+      {
+        method: "GET",
+        path: STATUS_PATH,
+        body: {
+          sha: "abc123",
+          total_count: 2,
+          statuses: [
+            { context: "build", status: "success" },
+            { context: "test", status: "failure" },
+          ],
+        },
+      },
+    ]);
+    const { stdout, exitCode } = await runCliTest(["pr", "checks", "5"], {
+      env: testModeEnv(server.url),
+    });
+
+    expect(exitCode).toBe(0);
+    expect(stdout).toContain("summary: 1 passed, 1 failed, 2 total");
+    expect(stdout).toContain("checks[2]{name,conclusion}:");
+    expect(stdout).toContain("  build,pass");
+    expect(stdout).toContain("  test,fail");
+    expect(stdout).toMatch(/^help\[\d+\]:/m);
+  });
+
+  it("renders a scalar checks line, not a list block, when no statuses are configured", async () => {
+    server = await startFixtureServer([
+      {
+        method: "GET",
+        path: PULL_PATH,
+        body: { number: 5, head: { sha: "abc123", ref: "feature" } },
+      },
+      {
+        method: "GET",
+        path: STATUS_PATH,
+        body: { sha: "abc123", total_count: 0, statuses: [] },
+      },
+    ]);
+    const { stdout, exitCode } = await runCliTest(["pr", "checks", "5"], {
+      env: testModeEnv(server.url),
+    });
+
+    expect(exitCode).toBe(0);
+    expect(stdout).toContain(
+      "checks: 0 passed, 0 failed — this PR has no CI checks configured",
+    );
+    expect(stdout).not.toContain("summary:");
+    expect(stdout).not.toMatch(/checks\[\d+\]\{/);
+    expect(stdout).toMatch(/^help\[\d+\]:/m);
+  });
+
+  it("maps every commit-status state and folds skipped/pending into the summary when non-zero", async () => {
+    server = await startFixtureServer([
+      {
+        method: "GET",
+        path: PULL_PATH,
+        body: { number: 5, head: { sha: "abc123", ref: "feature" } },
+      },
+      {
+        method: "GET",
+        path: STATUS_PATH,
+        body: {
+          sha: "abc123",
+          total_count: 5,
+          statuses: [
+            { context: "lint", status: "success" },
+            { context: "build", status: "failure" },
+            { context: "deploy", status: "warning" },
+            { context: "e2e", status: "skipped" },
+            { context: "docs", status: "pending" },
+          ],
+        },
+      },
+    ]);
+    const { stdout, exitCode } = await runCliTest(["pr", "checks", "5"], {
+      env: testModeEnv(server.url),
+    });
+
+    expect(exitCode).toBe(0);
+    expect(stdout).toContain("summary: 1 passed, 2 failed, 1 skipped, 1 pending, 5 total");
+    expect(stdout).toContain("checks[5]{name,conclusion}:");
+    expect(stdout).toContain("  lint,pass");
+    expect(stdout).toContain("  build,fail");
+    expect(stdout).toContain("  deploy,fail");
+    expect(stdout).toContain("  e2e,skip");
+    expect(stdout).toContain("  docs,pending");
+  });
+
+  it("reports a nonexistent PR as PR_NOT_FOUND with exit 1", async () => {
+    server = await startFixtureServer([
+      {
+        method: "GET",
+        path: "/api/v1/repos/testowner/testrepo/pulls/999",
+        status: 404,
+        body: { message: "Not Found" },
+      },
+    ]);
+    const { stdout, exitCode } = await runCliTest(["pr", "checks", "999"], {
+      env: testModeEnv(server.url),
+    });
+
+    expect(exitCode).toBe(1);
+    expect(stdout).toContain("code: PR_NOT_FOUND");
+  });
+});