When a user rapidly moves waypoints in the Planner, BRouter's
thread-priority watchdog kills older in-flight requests to free a thread
for newer ones, surfacing to the user as "operation killed by
thread-priority-watchdog" errors.
Two fixes:
1. Bump the BRouter thread pool on the dedicated host from 4 to 16.
`BROUTER_THREADS` is now a Dockerfile ENV (default 4 for
flagship/CI/dev) overridden to 16 in `infrastructure/brouter-host/`.
The host has 32 GB of RAM and idle cores; 4 threads was a flagship-era
constraint that no longer applies.
2. Cancel the previous in-flight `/api/route` request when a new one
starts. `use-routing.ts` now keeps an `AbortController` in a ref,
aborts it at the top of each `computeRoute`, and bails quietly on
`AbortError` so the newer call drives state.
Together these eliminate both the "real" contention (at the BRouter
level) and the wasted work (BRouter computing a route the client no
longer cares about).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
f283401076