Slate v2 Large-Document Broad Ops Batch

Goal

Make shell-backed large-document mode survive the first real broad operations:

• Ctrl+A
• paste over a full-document selection

without expanding all far islands into editable DOM.

Kept Work

• added large-document selection helpers in large-document-commands.ts
• wired the runtime path in editable.tsx
• passed shell-mounted island state down from editable-text-blocks.tsx
• expanded runtime proofs in runtime.tsx
• expanded the browser proof lane in replacement-huge-document-islands-benchmark.mjs

Runtime Rules That Landed

• Ctrl+A in large-document mode maps straight to the full document model range
• shell-backed selections stop trying to resolve a DOM range through unmounted islands
• paste on a shell-backed selection stays model-driven through ReactEditor.insertData(...)
• shell-backed paste fails closed on browser default fallback instead of letting the browser paste into the wrong mounted subset

Result

Runtime proofs

New runtime tests are green:

• EditableBlocks largeDocument maps Ctrl+A to a full-document model selection without expanding shells
• EditableBlocks largeDocument pastes over full-document shell-backed selection through the model

Breadth lane

pnpm bench:react:rerender-breadth:local stayed green:

• #3656: sibling leaves 0
• #4141: ancestors 0

Default huge-document lane

pnpm bench:replacement:huge-document:local at 1000 blocks stayed green:

• ready 514.31ms
• type 13.27ms
• select-all 3.27ms
• paste 34.21ms

Islands lane at 10000

pnpm bench:replacement:huge-document:islands:local:

• ready 557.22ms
• type 40.32ms
• select-all 26.60ms
• paste 35.71ms
• promote 51.40ms

Compared with the last clean non-islands 10000 baseline:

• ready 1229.49ms -> 557.22ms
• type 97.47ms -> 40.32ms
• select-all 34.36ms -> 26.60ms
• paste 190.48ms -> 35.71ms

That is a real broad-op win, not benchmark theater.

Remaining Gap

This still does not close the huge-doc typing gap fully.

The big remaining runtime job is active-corridor expansion beyond the default live island so deep interaction away from the top does not pay unnecessary promotion cost or fall back into awkward shell edges.