fix(github): fit the write mode cards and the repository hint on one row

The three write mode cards now sit on one row when the form is wide
enough and stack on a phone. The repository hint is shorter so the two
line clamp no longer hides its end behind a More link at 390 px.

Assisted-by: Claude:claude-sonnet-5-5 playwright

addons/github/ui/src/github.css

@@ -39,3 +39,6 @@
   background: var(--color-bg-secondary); white-space: pre-wrap; overflow-wrap: anywhere; max-height: 320px; overflow: auto;
 }
 @media (max-width: 480px) { .gh-prop__row { grid-template-columns: minmax(0, 1fr); gap: 0; } }
+
+/* Three cards on one row when they fit, one column on a phone. */
+.gh-mode-block .cn-cards { grid-template-columns: repeat(auto-fit, minmax(170px, 1fr)); }