feat(sessions): sandbox resource — per-session k8s Pod+PVC+Service (§4.15.4)

New X-Resource: sandbox on X-Service: sessions

POST ?session_id=  → CreateOrResume
  1. Ensure PVC workspace-session-<id> (Longhorn 1Gi)
  2. If pod already Running → return DNS (resume path, idempotent)
  3. Ensure pi-session-sandbox NetworkPolicy (shared, created once)
  4. Create Pod pi-session-<id> + Service pi-session-<id>:8787
  5. Wait up to 30s for Pod Ready
  6. Fire-and-forget: merge pod_name/pvc_name/svc_dns/last_active_at
     into session memory_entity summary

DELETE ?session_id= → delete Pod + Service + PVC

Idle reaper goroutine (5min interval, configurable via
SANDBOX_REAPER_INTERVAL_MINUTES): lists pi-session-* pods,
deletes Succeeded/Failed ones, preserves PVCs for resume.

Security: runAsNonRoot/1000, readOnlyRootFilesystem, drop ALL
caps, RuntimeDefault seccomp, automountServiceAccountToken:false.
Resources: 500m/512Mi req, 1/1Gi limit.
NetworkPolicy: egress → DNS + api:8080 only; ingress ← poimen-frontend.

RBAC: Role session-sandbox-manager + RoleBinding in poimen ns.
7 unit tests — all pass (mock k8s server).

Image: forgejo.riotpiao.com/riotpiao-poimen/poimen-pi-session-runtime:latest

internal/serviceadapter/session_adapter.go

@@ -102,6 +102,22 @@ func GetSessionSpec() *Spec {
 					},
 				},
 			},
+			// sandbox — per-session k8s Pod+PVC+Service lifecycle (§4.15.4)
+			{
+				Name: "sandbox",
+				Methods: []Method{
+					{
+						Verb:         "POST",
+						UpstreamPath: "/v1/sessions/sandbox",
+						Auth:         &Auth{Required: true, Capability: "sessions:write"},
+					},
+					{
+						Verb:         "DELETE",
+						UpstreamPath: "/v1/sessions/sandbox",
+						Auth:         &Auth{Required: true, Capability: "sessions:write"},
+					},
+				},
+			},
 		},
 	}
 }