fix(runner): allow short-form .svc DNS in credential fetch allowlist

BACKEND_API_URL is set to short-form Kubernetes service DNS
(e.g. ambient-api-server.ambient-code--ambient-s0.svc:8000) in OSD
deployments. The cluster-local security check only allowed
.svc.cluster.local, causing all credential fetches to be rejected.

Short-form .svc hostnames resolve only within the cluster and are
equivalent to .svc.cluster.local for security purposes.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: Ambient Code Bot

components/runners/ambient-runner/ambient_runner/platform/auth.py

@@ -122,6 +122,7 @@ async def _fetch_credential(context: RunnerContext, credential_type: str) -> dic
     parsed = urlparse(base)
     if parsed.hostname and not (
         parsed.hostname.endswith(".svc.cluster.local")
+        or parsed.hostname.endswith(".svc")
         or parsed.hostname == "localhost"
         or parsed.hostname == "127.0.0.1"
     ):