This commit includes two interdependent changes that must be applied
together:
- Treat `fit-content()` tracks as having an intrinsic min sizing
function when the limit resolves to zero.
- When clamping growth limit to fit-content limit, use `max(base_size,
fit_content_limit)` instead of just `fit_content_limit` to preserve
intrinsic sizing contributions.
These changes are coupled because the first change causes
`fit-content(0)` tracks to participate in intrinsic sizing, while the
second ensures the base size from that sizing is not discarded during
clamping.
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