* studio/frontend: compare composer blocks send when no model picked
Closes the racing-handle half of #5569. In Compare mode (GeneralCompare
shell with model1/model2 props), if the user sends a prompt before
picking models in either pane, the SharedComposer used to fall through
to the per-handle append branch. Both panes then raced
createOpenAIStreamAdapter -> autoLoadSmallestModel, one won, the other
dispatched into an unloaded slot and produced an empty bubble with a
1000000.0 tok/s readout. The per-pane picker state never observed the
global checkpoint change either, so both pickers stayed at
"Select model".
Add a guard before the content build: when handlesRef has model1/model2
keys but both selections are empty, surface a toast asking the user to
pick models first, leave the text in the composer for retry, and never
enter the racing dispatch path. Keeps the per-pane picker state as the
source of truth for which model is on each side.
The unphysical tok/s readout that the same path produced is separately
covered by PR #5570 (display guard).
* studio/frontend: tighten compare-mode guard to require both panes
Review feedback on #5574:
- Gemini: the redundant `model1 !== undefined && model2 !== undefined`
checks let the racing-handle dispatch slip through whenever the
Compare props arrive as undefined, which is the exact case the
guard is trying to block.
- Codex: with `isGeneralizedCompare` keyed on `model1?.id || model2?.id`,
a half-selected Compare (one model picked, one empty) still falls
into the generalized branch. The composer clears, the empty pane
gets the user message appended, and `startRun` only fires for the
side with an id, leaving the empty pane with a dangling prompt
and no response.
Switch `isGeneralizedCompare` to require BOTH panes (`&&`), drop the
undefined gate, and surface the "Pick a model in each pane" toast for
either the fully-empty or half-selected case. `hasCompareHandles` is
true only inside GeneralCompareContent, so LoraCompare and the
single-pane path stay unchanged.
* studio/frontend: shorten compare-mode no-model-guard comment
* studio/frontend: clarify compare-pane toast wording
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Co-authored-by: danielhanchen <michaelhan2050@gmail.com>
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