…API clients (#3874)

## Summary

During `trigger()` worker-queue resolution, `getWorkerQueue` wrapped any
error from `getDefaultWorkerGroupForProject` into a client-facing
`ServiceValidationError` (HTTP 422) carrying `error.message`. That
method runs `project.findFirst` on the **writer**; when the writer is
unreachable Prisma throws a connection error (P1001) whose message
includes the database host, and that raw message was returned to the API
client and surfaced in the run view via the SDK's `TriggerApiError`.

It also mis-classifies a transient outage: a 422 is not retried by the
SDK, so triggers failed permanently instead of riding out a brief writer
blip.

## Design

This is the only place on the trigger path that folds a *caught* error's
message into a client-facing error — every other DB failure on the path
propagates to the route's generic 500 handler (scrubbed, and retried by
the SDK). So the fix is local:

- Add `isInfrastructureError()` — true for Prisma connection-level
failures (the DB-unreachable family: P1001/P1002/P1008/P1017, plus the
init/panic/unknown client error classes), false for query/validation
errors (e.g. P2002).
- At the wrap site, rethrow infrastructure errors so they reach the
generic 500 handler (no raw message, and retryable). Genuine domain
failures (e.g. "Project not found.") still become a 422.

Only P1001 ("can't reach database server") has been observed in
practice; the rest of the connection family is included as same-class
forward-proofing.

## Test plan

- [x] Unit: `isInfrastructureError` classifies a P1001 (incl. the Prisma
6.x `PrismaClientKnownRequestError` shape) and init errors as
infrastructure; P2002 and a plain `Error` as not
- [x] `getWorkerQueue` rethrows a P1001 unchanged instead of wrapping it
in a `ServiceValidationError`; still wraps a domain failure as a
`ServiceValidationError` — RED on current code, GREEN after
- [ ] (optional) toxiproxy e2e: trigger with the writer cut → HTTP 500
generic body, no DB host in the response

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Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>