feat(plc): ephemeral soft-PLC provisioning + program load (#183)

Dynamic PLC testing without reaching the customer's device: when a PLC/SPS
target ships control logic but no reachable live URL, instantiate that logic
ourselves on a throwaway OpenPLC container in-cluster, load + start it, probe
the provisioned Modbus endpoint, and tear it down. No customer network access,
sandboxed, and reproducible.

This is the phase-1 foundation of epic #183 (OpenPLC substrate). It covers:

- provision: ephemeral container lifecycle (docker CLI). Resource-capped
  (memory/cpus/pids), hardened (no-new-privileges), labelled, joined to the
  agent's own network with no host port exposure, and swept by a stale reaper
  for anything a crashed run leaks. The `docker` argv is built by pure functions
  so it is unit-tested without a daemon.
- openplc: drives the OpenPLC web UI to load a program — login → upload →
  save → compile (MatIEC) → start_plc (which opens Modbus/TCP 502).
- runtime::provision_and_test: composes them under a hard deadline with
  guaranteed teardown on every path (success / error / timeout), then runs the
  existing ICS probe against the provisioned endpoint. extract_program picks the
  best loadable program (complete ST > largest ST > PLCopen XML).
- orchestrator: for a PlcSps target with control logic and no live URL, run
  provision-and-test after the static PLC scan. Gated by PlcRuntimeConfig
  (PLC_RUNTIME_ENABLED, default off — needs Docker access in the agent).

DAST-against-WebVisu and CODESYS-runtime fidelity are follow-ups.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.env.example

@@ -34,6 +34,19 @@ SCAN_SCHEDULE=0 0 */6 * * *
 CVE_MONITOR_SCHEDULE=0 0 0 * * *
 GIT_CLONE_BASE_PATH=/tmp/compliance-scanner/repos
 
+# Dynamic PLC testing — ephemeral soft-PLC provisioning (#183). Off unless
+# enabled; requires the agent container to have Docker access (socket mount).
+# When on, a PLC/SPS target with control logic but no reachable device gets its
+# logic instantiated on a throwaway OpenPLC, probed, then torn down.
+PLC_RUNTIME_ENABLED=0
+PLC_RUNTIME_IMAGE=registry.meghsakha.com/openplc:latest
+PLC_RUNTIME_NETWORK=certifai
+PLC_RUNTIME_MEMORY=512m
+PLC_RUNTIME_CPUS=0.5
+PLC_RUNTIME_MAX_LIFETIME_SECS=180
+PLC_RUNTIME_OPENPLC_USER=openplc
+PLC_RUNTIME_OPENPLC_PASSWORD=openplc
+
 # Dashboard
 DASHBOARD_PORT=8080
 AGENT_API_URL=http://localhost:3001