🐛 fix(dom): lock threaded tree reads

[gaborbernat]

Free-threaded readers crashed while one thread walked child, sibling, or attribute arrays and another rewired the same tree.

The fix takes the existing tree lock around lazy node-axis cursor movement, sequence snapshots, and attrs view materialization.

[codspeed-hq]

Merging this PR will not alter performance

✅ 91 untouched benchmarks
⏩ 18 skipped benchmarks¹

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_{Comparing gaborbernat:fix/threaded-tree-access (4e86478) with main (83cc16c)}

Footnotes

1. 18 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩