Ignacy Łątka aa13120abf fix(screenshot): wait for first frame so multi-sim captures don't fail (#391) (#399) ...

After more investigation i've found a much better fix for #391. 
I'm merging this either way, because it blocks 0.13.0 release and we
already have this fix tested and approved.
By the next release, I want to revert this patch in favour of fixing
core of the issue in simserver.

Regression introduced by
https://github.com/software-mansion/radon/pull/101 adding the streaming
feature to the argent simulator-server build, which made
`/api/screenshot` serve the last streamed frame async instead of
capturing on demand.

<details>

## Summary

Fixes #391 — `screenshot` failing with `no image to export` when more
than one simulator is booted, even with an explicit `--udid`. Regression
in 0.12.x.

## Root cause

The simulator-server captures screenshots from its **live frame
stream**, so a capture only succeeds once the first frame has arrived.
Immediately after the server starts streaming, `POST /api/screenshot`
replies `HTTP 200 { error: "no image to export" }` until that first
frame lands (~0.5–1s). The tool-server requested the capture right after
the server became ready, **losing that race**.

- With a single, foreground simulator the first frame arrives fast
enough that the race is usually won — hiding the bug.
- With more than one simulator booted, the target is often backgrounded
and its first frame is delayed, so the race is lost **reliably** → `no
image to export`.

This became reachable when streaming was enabled for the argent
simulator-server build in 0.12.x (radon
[#101](https://github.com/software-mansion/radon/pull/101)); the 0.11.0
non-streaming build captured frames on demand, so it was immune. Device
selection itself is correct — each device's stream captures the right
device (verified: Pro Max → 1320×2868, iPhone 15 → 1179×2556).

## Fix

`httpScreenshot` now polls past that specific transient (every 250ms, up
to 6s) instead of failing immediately, while still surfacing every other
error (non-2xx, Android `wrong data size`, missing url/path) right away.

## Verification

End-to-end against the **shipped** simulator-server binary with
**three** booted simulators, forcing a fresh sim-server spawn before
each capture:

| | result |
|---|---|
| **unfixed** (current `dist`) | `no image to export` ~2/3 of
fresh-spawn attempts |
| **fixed** | 7/7 success (~800ms), returns a correct PNG (1320×2868) |

- `npm test` (tool-server): **1199 passed**, including new retry /
give-up cases for `httpScreenshot`
- `npx tsc --build`, `prettier --check`, `typecheck:tests`: clean

</details>

2026-06-24 21:00:54 +02:00

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