Reverts the tooltip half of 4798994dc; keeps the idle-cost scenario.
Lazily mounting Radix on first hover measured well (105k -> 26k
TooltipProvider renders per drag) but broke 18 tests across 12 files.
Those tests are not incidental: the repo has an established convention of
asserting `[data-slot="tooltip-trigger"]` at mount to prove a control
carries a tooltip, and deferring the mount invalidates all of them at
once. There is also a real behavior risk the convention was protecting —
`asChild` puts the slot on the button element itself, so arming REPLACES
the node, which is exactly the kind of identity change that breaks focus
restoration and ref-holding call sites.
A 4x cut in tooltip churn is not worth reworking every tooltip assertion
in the app plus taking that risk, on a component with ~107 call sites.
If it's worth revisiting, the right shape is probably making
TooltipProvider itself cheap (one app-level provider) rather than
deferring the mount per call site — that preserves the DOM contract these
tests encode.
The genuine win in this branch stands on its own: the $layoutTree
subscription fix (commits 83 -> 12 on a sash drag) is unaffected.
Brooklyn Nicholson
0226d1162e