Respect text-wrap-mode when line breaking around inline boxes

[nicoburns]

LLM Contributions: This PR was written by Devin (analysis, code, and description).

Fixes 10 WPT css-flexbox reftests in Blitz (flexbox_flex-{0,1,N}-0-{N,Npercent,auto}-shrink.html and flexbox_flex-basis.html) whose reference pages use white-space: nowrap on a block containing only adjacent inline-block spans. Parley wrapped the boxes anyway.

Two problems:

1. The line breaker unconditionally marks a break opportunity after every inline box, ignoring TextWrapMode::NoWrap.
2. The breaker's wrap-mode state (LineState::text_wrap_mode) is only updated lazily from text clusters, so in a layout containing only inline boxes and no text it stays at the default Wrap and the container's nowrap never takes effect.

Fix:

• Add LayoutData::default_text_wrap_mode, set from the first resolved style in build_into_layout and overridden by TreeBuilder::build_into with the tree root style's wrap mode (with no text, the style table only contains a synthesized default style, so the root style must be taken from the tree builder).
• Initialize BreakerState.line.text_wrap_mode from it in BreakLines::new, and only mark a break opportunity after an inline box when the current wrap mode is Wrap.
• Use the same initialization in calculate_content_widths, so the min-content width of nowrap box-only content is the sum of box widths rather than the max.

Verified against Blitz's WPT runner (same change applied to parley 0.10 via a Cargo patch override): css/css-flexbox pass count goes 654 → 664 with zero regressions.

Changelog

Fixed

• Inline boxes no longer create line break opportunities when text-wrap-mode is nowrap.

Link to Devin session: https://app.devin.ai/sessions/844c19c6f8394d5bbb88b577c1f0558e
Requested by: @nicoburns

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