Three follow-ups to the browser defaults:

The dimension inputs were bare `Input type=number` at w-16, which clipped
4-digit values ("1280" rendered as "128("). They are now `NumberField`, the
repo's real numeric control, widened to fit and with grouping switched off so
a height reads "1024" rather than "1,024".

They commit on blur via `onValueCommitted` instead of per keystroke. Typing
"2560" passes through "256", which is itself a legal dimension, so a
change-handler would persist that intermediate size and rewrite settings on
every key.

Adds an orientation control next to the dimensions, reusing the device
toolbar's rotate affordance — its icon moves to a shared module rather than
being duplicated. Rotating a preset keeps the preset: `resolvePreviewViewport`
already stores rotated presets as the id plus swapped dimensions, so a rotated
iPad Mini stays an iPad Mini instead of decaying into a custom size.

Adds `browserAutoShowFloatingPreview` (on by default) for whether an
agent-opened preview pops the floating player into view. An explicit
`open`/`show` on `preview_open` still wins: that is the agent deliberately
surfacing or hiding its work, which shouldn't be overridden by a default.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>