feat(api): reserve HealthStatus enum + health field on ContainerSnapshot

Sources/ContainerResource/Container/ContainerSnapshot.swift

@@ -39,16 +39,25 @@ public struct ContainerSnapshot: Codable, Sendable {
     public var networks: [Attachment]
     /// When the container was started.
     public var startedDate: Date?
+    /// The most recently observed health of the container.
+    ///
+    /// At present the daemon does not run a container-level healthcheck
+    /// observer, so this field is always `nil`. The shape is reserved so that
+    /// downstream tools (e.g. `compose`) have a stable type to read from once
+    /// a healthcheck observer is wired into the API server.
+    public var health: HealthStatus?
 
     public init(
         configuration: ContainerConfiguration,
         status: RuntimeStatus,
         networks: [Attachment],
-        startedDate: Date? = nil
+        startedDate: Date? = nil,
+        health: HealthStatus? = nil
     ) {
         self.configuration = configuration
         self.status = status
         self.networks = networks
         self.startedDate = startedDate
+        self.health = health
     }
 }

Sources/ContainerResource/Container/HealthStatus.swift

@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2026 Apple Inc. and the container project authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//===----------------------------------------------------------------------===//
+
+import Foundation
+
+/// The observed health status of a container, as derived from a periodic
+/// healthcheck probe.
+///
+/// At present the daemon does not run a container-level healthcheck observer,
+/// so ``ContainerSnapshot/health`` is always `nil`. This type is reserved for
+/// downstream tools (e.g. `compose`) that want a stable shape to read from
+/// once a healthcheck observer is wired into the API server.
+public enum HealthStatus: String, CaseIterable, Sendable, Codable {
+    /// No healthcheck has been configured or no result is yet available.
+    case none
+    /// The healthcheck is running but has not yet produced a successful probe.
+    case starting
+    /// The most recent probe(s) reported the container as healthy.
+    case healthy
+    /// The most recent probe(s) reported the container as unhealthy.
+    case unhealthy
+}