fix(mobile): list bullets keep a gap before their text at every text size#26268

In assistant messages, a list bullet sat almost against its text ("•Moonbase"), and touched it at large text sizes. Our list style set a 6 pt gap, half the markdown library's default. The bullet is drawn centred on the gap's edge, so only about 3 pt showed. The bullet grows with the system text size and the gap did not, so at the largest sizes the bullet closed it.

The gap is now the library's default 12 pt, scaled by the system text size (useWindowDimensions().fontScale), so bullet and text keep the same spacing at every size.

Full screens from vp run mobile:e2e on the Simlock pool, before (left) and after (right).

Pixel 10 Pro, largest text:

Pixel 10 Pro largest text, before and after

iPad Pro 13", landscape, largest text:

iPad largest text, before and after

iPhone SE, default text size:

iPhone SE default text, before and after

Pixel Tablet, default text size:

Pixel Tablet default text, before and after

🤖 Generated with Claude Code — Claude Opus 5.5