Phase 5 of PRD 0014. End-to-end test against real Docker:
- Brings up a cred-proxy sidecar with route /a/ → unreachable
upstream (so 502 = route matched, 404 = no route).
- Calls apply_routes_change to swap to /b/ only.
- Polls until the route table flips: /a/ now 404s, /b/ now 502s.
- Separately verifies fetch_current_routes returns the live file,
apply with invalid JSON raises, and apply against a non-existent
sidecar raises.
No fake-upstream container needed: unreachable hostnames give the
502 signal directly. apply_routes_change uses docker exec / cp / kill
(not bind mounts), so this should work in docker-in-docker too —
no DinD skip needed.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
