test: share the first-page and clock helpers

writeFirstPage answers paged listings in app and services tests,
testNow replaces the copied clock, withoutANSI the second color
stripper, and the single-entry table test becomes a plain test.

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

internal/app/issue_attachments_test.go

@@ -105,7 +105,7 @@ func TestAttachmentTablesDownloadsAndDoneLines(t *testing.T) {
 	}))
 	defer server.Close()
 	deps, out, diagnostics := serverDeps(t, server.URL)
-	deps.Now = func() time.Time { return time.Date(2026, 10, 11, 20, 0, 0, 0, time.UTC) }
+	deps.Now = func() time.Time { return testNow }
 	deps.Getenv = serverEnv(server.URL, map[string]string{"NO_COLOR": "1"})
 	plainOutput(t, deps)
 	run := func(tty bool, args ...string) error {