feat: reachability and consumer profiles (SAND-WP-0011)

Add reachability enrichment (tunnel metadata, ops-bridge pointer),
secret_refs boundary resolution, profile.agent-dev and profile.build,
CLI reachability show, API endpoint, consumer smoke scripts, and tests.

profiles/profile.agent-dev.yaml

@@ -0,0 +1,42 @@
+id: profile.agent-dev
+version: "1.0.0"
+extension: ext.compose-ssh
+route:
+  strategy: prefer-self-hosted
+  extensions:
+    - ext.compose-ssh
+    - ext.e2b
+    - ext.modal
+    - ext.saas-stub
+  max_cost_per_hour_usd: 1.0
+isolation:
+  level: container
+network:
+  default: deny
+  egress: []
+workspace:
+  mode: remote-canonical
+  access: rw
+scope_default: agent
+ttl:
+  default: 8h
+  max: 24h
+  idle_reap: 2h
+resources:
+  cpu: null
+  memory_mb: null
+setup:
+  instructions: >
+    Agent development sandbox for glas-harness. Prefer self-hosted compose;
+    burst to cloud when host unavailable. Consumer actor: agt.
+  secret_refs: []
+placement:
+  prefer: [sandboxer01]
+  fallback: [coulombcore]
+reachability:
+  tunnel: ops-bridge
+  identity: ops-warden
+metadata:
+  cost_class: self-hosted
+  latency_class: standard
+  observability: none