v1.64.0

Added

• progressHeader covers the last two values a forked bar needed. backButtonStrokeWidth (chevron stroke weight, default 2) — backButtonSize covered the glyph's size but not its weight, and at a 20pt glyph the difference between 2 and 2.5 reads as "the icon changed" without anyone being able to say why. paddingTop (space above the bar, default 0) — the block had paddingBottom but nothing for the top, so a fork's extra space above the bar had no expression and the header sat higher after retirement.
• paddingTop is added to the top safe-area inset rather than replacing it. The inset is not optional, so a field that replaced it would let a payload push the header under the notch. paddingBottom has no inset to compose with, which is why only this one is additive — the asymmetry is spelled out in the type, the renderer and the docs.

Notes

• Both default to the previous values, so nothing moves for anyone not setting them.
• One structural difference is documented rather than fixed. The header is a three-column row (back button / track / right spacer, flex 1 / trackFlex / 1) and the reserved right column cannot be removed, so a fork whose track runs to the right padding edge will see its right end pull inward after retirement. trackFlex shrinks that column proportionally but never to zero. Removing it means a two-column mode — a layout change rather than another optional prop — so it deserves its own decision. Net: a forked bar is retirable at a cost, not at parity.

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