feat(lab): LineClamp — clamp arbitrary content to N lines (port from XDSLineClamp)

Summary

Add a LineClamp component that truncates arbitrary content to a fixed number of lines with an ellipsis, ported from the internal XDSLineClamp component. Port the value and behavior, not the internal structure.

Why a dedicated component

Astryx already clamps text via Text's maxLines prop (backed by useTruncation). LineClamp is a different primitive: a standalone wrapper that clamps whatever you put inside it to N lines — not just a Text node.

So this is not a duplicate of Text — it's the reusable clamp primitive that other components and consumers can wrap around content that isn't a single Text.

Proposed behavior (to confirm against the internal source during the port)

• lines (or maxLines) — number of lines to clamp to.
• Clamps via -webkit-line-clamp (the same mechanism Text/useTruncation already rely on), with a block/overflow setup that works cross-browser.
• Truncation detection should reuse the existing useTruncation hook rather than reinventing overflow measurement — it already handles the multi-line Range.getBoundingClientRect() case and shares a single ResizeObserver.
• Optional tooltip / "show more" affordance on overflow (mirror what the internal component does; decide during the port).
• Extends BaseProps, xstyle/className/style escape hatches, displayName, 'use client'.

Scope

• Land in @astryxdesign/lab first (canary-only), following the standard lab → core graduation path.
• Full component surface: LineClamp.tsx, colocated LineClamp.test.tsx, LineClamp.doc.mjs, index.ts export, Storybook story, showcase block.
• Reuse useTruncation and semantic tokens; StyleX only.

Open questions for the port

• Prop name: lines vs maxLines (align with Text's existing maxLines for consistency?).
• Does the internal component own the overflow-detection/tooltip behavior, or is that left to the consumer? Decide what to port vs. drop.
• Any semantic-name/API differences from the internal version get resolved to Astryx conventions (port the value, not the internal API shape).

Acceptance criteria

• LineClamp clamps arbitrary children to N lines with an ellipsis.
• Reuses useTruncation for overflow detection (no reinvented measurement).
• StyleX only, tokens, BaseProps escape hatches, displayName, 'use client'.
• Colocated test, .doc.mjs, Storybook story, showcase block, index.ts export.
• Lands in @astryxdesign/lab; documented as lab/canary.