fix: reconcile the pull request stream

Share one shortSHA helper, keep Markdown raw in view tests through the
markdown preference, and drop rawWindow now that pull request lists use
the paged helpers.

Signed-off-by: bircni <bircni@icloud.com>

internal/app/pulls_test.go

@@ -57,7 +57,7 @@ func TestPullListTable(t *testing.T) {
 	require.Equal(t, "17\tImprove greeting\tbob:bob/greeting\topen\tbob\t2026-10-11T10:00:00Z\n15\tWIP: experiment\texperiment\tdraft\talice\t2026-10-11T09:00:00Z\n", out.String())
 
 	out.Reset()
-	plainTTY(&deps, server.URL)
+	plainTTY(t, &deps, server.URL)
 	require.NoError(t, Execute(context.Background(), deps, []string{"pr", "list", "-R", "alice/project"}))
 	require.Equal(t, `Showing 2 of 2 open pull requests in alice/project