Slate v2 Active-Corridor Promotion Batch

Goal

Make shell promotion turn into real editing, not just a visual state change.

That means:

• promote a far island
• move model selection into that island
• focus the real editor root
• prove that typing after promotion works in the promoted island

Kept Work

• shell mouse-down now promotes and focuses the editor root in island-shell.tsx
• EditableBlocks promotion now selects the start of the promoted island in editable-text-blocks.tsx
• runtime proof extended in runtime.tsx
• browser proof extended with promoteTypeMs in replacement-huge-document-islands-benchmark.mjs

Result

Runtime proof

EditableBlocks largeDocument promotes a shelled island on mouse down now proves:

• shell disappears
• selection lands at the promoted island start
• mounted text count narrows to the promoted island when activeRadius=0

Browser proof at 10000

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

• ready 541.03ms
• top typing 37.95ms
• promote only 95.38ms
• promote then type 36.49ms
• select-all 28.02ms
• paste 34.63ms

This is the first proof that deep interaction away from the default live island can stay cheap enough to keep.

Default huge-doc lane stayed green

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

• ready 508.19ms
• type 12.80ms
• select-all 2.72ms
• paste 33.22ms

Verdict

The large-document layer is no longer top-of-document-only theater.

Promotion now creates a real active corridor entry point for remote editing.

The next batch is corridor widening and policy:

• decide the right default activeRadius
• keep neighboring islands live when needed for editing comfort
• avoid paying ~95ms promotion cost more often than necessary