## Why
Diagnostic reports can span several envelopes, and the previous 10-second shared
network budget could expire before slow uploads and their attachments completed.
## What changed
- Give each diagnostic report a single five-minute deadline shared by the event,
attachments, retries, and retry backoff.
- Stop reading or sending later attachments once the deadline or a Sentry rate
limit is reached.
- Limit the app server to three concurrent report uploads and return an
overloaded JSON-RPC error for additional requests until a slot is released.
## Testing
Add coverage for slow multi-envelope reports, deadline-aware retries, skipped
attachments, rate-limit handling, and concurrency-slot release after failures.
GitOrigin-RevId: bdacf6c9731df16d2763e204565986eb6d540233
chess
a17ee5705c