feat(host-agent): Phase 2 — Dune docker-compose adapter via Supervisor trait

Introduce a Supervisor trait (async-trait) so the agent manages games with
different models behind one wire contract. ProcessSupervisor (spawned process:
rust/conan/soulmask) and the new DockerComposeSupervisor (dune) both impl it;
Agent.supervisors is now HashMap<String, Arc<dyn Supervisor>> and instancecmd
dispatch is game-agnostic — start/stop/restart/status identical across games,
selected by a per-game factory in main. InstanceState moved to the shared
supervisor module.

DockerComposeSupervisor drives docker-compose up-d / stop / restart against
the instance's compose project, with -f/-p/single-service support and a
configurable compose binary. New [instance.docker_compose] config block.
First cut = lifecycle + cached state; container crash-detection + restart
adoption deferred to Phase 3b (reconcilable with a compose ps probe).

Trait choice (dyn over enum) per Commander: scales to future planes (kubectl,
AMP/podman, SSH) as new struct+impl, no central match.

56 tests green (6 new docker-compose mock-binary tests + 5 refactored process
tests), zero warnings. Live verification pending a real Dune stack.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

corrosion-host-agent/src/main.rs

@@ -5,8 +5,8 @@
 //! game adapters arrive in Phase 1+ (see PROTOCOL.md).
 
 use corrosion_host_agent::{
-    agent, bus, config, filemanager, hostcmd, instancecmd, prober, process, subjects, telemetry,
-    version,
+    agent, bus, config, docker_compose, filemanager, hostcmd, instancecmd, prober, process,
+    subjects, supervisor, telemetry, version,
 };
 
 use anyhow::{Context, Result};
@@ -92,10 +92,20 @@ async fn run(settings: config::Settings) -> Result<()> {
 
     let nats = bus::connect(&settings).await?;
 
-    let supervisors = settings
+    // Per-game supervisor factory: container-managed games (Dune) get a
+    // docker-compose supervisor; everything else is a spawned-process
+    // supervisor. Both satisfy the `Supervisor` trait, so the rest of the agent
+    // is game-agnostic.
+    let supervisors: std::collections::HashMap<String, Arc<dyn supervisor::Supervisor>> = settings
         .instances
         .iter()
-        .map(|inst| (inst.id.clone(), process::ProcessSupervisor::new(inst)))
+        .map(|inst| {
+            let sup: Arc<dyn supervisor::Supervisor> = match inst.game.as_str() {
+                "dune" => docker_compose::DockerComposeSupervisor::new(inst),
+                _ => process::ProcessSupervisor::new(inst),
+            };
+            (inst.id.clone(), sup)
+        })
         .collect();
 
     let agent = Arc::new(Agent {