## Summary

Fixes the 6 `TimeoutError: locator.click: ... element is not enabled`
failures in `chat_tabs.spec.ts` and `per_chat_input.spec.ts` on CI run
[24692456779](https://github.com/dyad-sh/dyad/actions/runs/24692456779)
caused by a Lexical/jotai race during chat switches.

## Root cause

Trace + screenshot from the failing shards show chat 2 with an empty
input and a disabled Send button the moment the second `sendPrompt()`
runs. The race:

1. `clickNewChat()` navigates to chat 2 (`selectedChatIdAtom` flips, URL
updates, `ChatInput` re-renders with `chatId=2`).
2. Playwright's `fill()` into the Lexical editor fires
`OnChangePlugin.onChange` before React has flushed the atom update for
this render cycle.
3. `chatInputValueAtom`'s writer is keyed off `selectedChatIdAtom`, so
the typed text gets stored under the **previous** chat's slot.
4. On the next render `ExternalValueSyncPlugin` sees `value=""` for chat
2 and resets the editor to empty.
5. `inputValue.trim()` is empty → Send button stays `disabled` → 30s
click timeout.

Only the *second* `sendPrompt()` after a `clickNewChat()` fails, and
it's flaky because it depends on render/event ordering.

## Fix

Wrap `click → fill` in `expect.toPass()` and assert the editor actually
contains the prompt and the Send button is enabled before clicking. On a
dropped fill the loop re-runs once atoms settle, eliminating the race
deterministically. No product changes.

## Test plan

- [x] `npm run fmt && npm run lint && npm run ts`
- [ ] CI: chat_tabs.spec.ts and per_chat_input.spec.ts pass on shards
1/2

🤖 Generated with [Claude Code](https://claude.com/claude-code)
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Co-authored-by: Will Chen <7344640+wwwillchen@users.noreply.github.com>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>