[bitsandfoxes]

Fixes the flakes that still failed CI runs on top of the stack, each traced to its cause.

• Unsymbolicated native frames. sentry-cli debug-files upload returns before sentry.io has processed the files. In run 39645739252 the macOS GameAssembly debug companion was uploaded at 17:54:36 and listed by the server at 17:57:27; the crash event came in at 17:56:02, was symbolicated without it and never reprocessed. assert-symbol-upload.ps1 now polls files/dsyms/?debug_id= until each uploaded debug companion, IL2CPP mapping and source bundle is listed (portable PDBs count via their embedded sources feature), for at most 300 s. A timeout, a missing token or a 401/403 is a ::warning::, not a failure. The assert steps get SENTRY_AUTH_TOKEN for that (Compile iOS gets it as a new workflow_call secret).
• iOS first launch hangs. Over 62+ Run iOS legs, a first launch less than 100 s after the simulator boot stalled in 6/12 legs, 100–130 s in 1/11, at 130 s or later in 0/51; waiting for simctl bootstatus doesn't help (Skip the iOS simulator terminate right after boot and bound the others app-runner#65). Run iOS now starts with Build iOS, boots the simulator while Compile iOS runs, and waits for the app artifact with wait-for-artifact. When the artifact is already there (a rerun), the first launch waits until 150 s after boot. Job timeout 25 → 45 min to cover the wait.
• Crash report dropped on a sentry.io 5xx. sentry-cocoa deletes an envelope that the server answers with a 5xx (Received response status code: 503 in run 40264124350), so the crash event never arrives. crash-capture now reruns once per job when the send output shows a 5xx.
• Unity 6000.6 build killed with exit 137 in Docker. Unity 6000.6 kills the PID in Library/burst.pid at startup. The project comes from Create in another container, where that PID was 259; in the build container PID 259 is the xvfb-run wrapping the editor (run 40275305182). The orphaned editor then failed the retry with "another Unity instance is running". build-project.ps1 removes Library/*.pid before building.
• A retried configure-and-build launch built without Sentry's options configuration. OptionsConfigurationItem.SetScript re-created the configuration asset on every ConfigureOptions. On 6000.6 AssetDatabase.CreateAsset destroys the old object, and ??= kept the destroyed reference; on 2021.3 the reference stays live but no longer points to the asset. Either way, a second ConfigureOptions saved OptionsConfiguration/CliOptionsConfiguration as {fileID: 0}, so the build had no auth token (seen in run 40314070230 attempt 10, when the shutdown-crash retry re-ran that launch). SetScript now reuses the asset already at the path; EditMode tests cover both references, and fail before on both Unity versions. Users running ConfigureOptions twice hit the same bug, so it has a CHANGELOG entry.
• Two gaps on the retry path. The symbol-upload assertion now accepts sentry-cli's File upload/processing complete, which is all a rebuild prints when every chunk is already on sentry.io, and fails on some symbols did not process correctly. The shutdown-crash retry now also fires on exit 133 (SIGTRAP) after Batchmode quit successfully invoked, for a shutdown stall that kills Unity before it logs the signal.

Stacked on #2910.

CI evidence: run 40314070230, rerun in full back to back on 383a6c3 (before the last three commits): 8 of 10 attempts green on the first try, p50 32.0 / p90 35.2 min for the green ones (baseline 41 / 80). All 20 symbol waits in attempt 1 finished in 0–14 s, none timed out. The two red attempts:

• Attempt 8, Build Android 6000.6: a Unity-internal Bee error (Request cancelled while reading the binlog) reported as compiler errors without compiling. First sighting in 26 runs.
• Attempt 10, Build Linux 6000.6: the shutdown-crash retry of the configure-and-build launch ran ConfigureOptions a second time. OptionsConfigurationItem.SetScript re-creates the configuration assets, and ??= keeps the deleted objects, so both references were saved as {fileID: 0} and the build had no auth token. Fixed in this PR (see above).

A throwaway commit (since dropped) that ran the configure-and-build launch twice in every build job, as a retry would: run 40386193023 is green in 33.2 min, and every build called CliConfiguration::Configure() on the second launch with no Auth Token missing. The clean head: run 40391327148 is green on the first attempt in 27.3 min.

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