Pulls in the extra commit pushed to PR #1381 after our initial absorb. Adds a
@media (max-width: 340px) block that compacts gutters (composer-wrap padding,
composer-footer gap, composer-left gap) without shrinking the 44px touch
targets. Plus its regression test.
Verified with apply --check failed but actual apply succeeded — the failure
was due to context drift from our earlier CSS specificity fix; the new lines
landed at the correct location. test_mobile_layout.py: 47 tests passing.