feat: update Taffy revision

[hyfdev]

Summary

• pin Taffy to upstream main revision 8d13fdc8
• map scrollable overflow, detailed Grid positions and line names, and containment
• regenerate bindings and update tests, website docs, and PCR records

Validation

• pnpm vp run check
• pnpm vp run check:wasm
• 238 shared Core tests pass on Node and Wasm
• Yoga suite remains 557 passed, 84 expected failures, and 17 skipped

Benchmark note

Three website benchmark refresh attempts were rejected by the existing stability gates in different scenarios. No unstable dataset was written; the pending refresh and retained dataset source are recorded in technology-stack.md.

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[hyfdev]

Adversarial review complete.

• Audited all 18 upstream commits between the old and new Taffy revisions, including public structs, feature closure, transitive dependencies, TaffyTree/NodeId signatures, panic boundaries, and generated transports.
• Exercised every Contain value plus invalid numbers and non-number inputs; failures remain controlled and updateStyle remains atomic.
• Exercised Detailed Grid under RTL with positive implicit tracks and named lines. This exposed a missing regression case, now covered by commit 271dc13.
• Corrected the squash title from chore to feat so the Core release planner can select a version without marking the change breaking.
• Verified no stale old revision, contentSize, sizes/gutters, wire-v1, or 21-slot Layout references remain outside intentional migration/history text.
• Re-ran pnpm vp run check and pnpm vp run check:wasm: 238 Core tests pass on native and Wasm; Yoga remains 557 passed, 84 expected failures, 17 skipped. All GitHub checks pass on Ubuntu, Windows, Wasm, Node, Rust, and PR title.

No remaining review findings or merge blockers.