Merge branch 'feat/plugin-acquire-lease-agent-id' into dev

Thread agentId into PluginEnvironmentAcquireLeaseParams + host call sites
so plugin-backed sandbox providers (e.g. paperclip-plugin-k8s) can scope
lease state per-agent without needing an SDK callback or DB lookup.

server/src/__tests__/heartbeat-plugin-environment.test.ts

@@ -209,6 +209,7 @@ describeEmbeddedPostgres("heartbeat plugin environments", () => {
       issueId: null,
       config: { template: "base" },
       runId: run!.id,
+      agentId,
       workspaceMode: "shared_workspace",
     });
     await vi.waitFor(() => {
@@ -426,6 +427,7 @@ describeEmbeddedPostgres("heartbeat plugin environments", () => {
       issueId,
       config: { template: "new" },
       runId: run!.id,
+      agentId,
       workspaceMode: "shared_workspace",
     });
   }, 15_000);