feat(cli+docs): mcpctl get agent KIND/STATUS columns + virtual-agent smoke + docs (v3 Stage 4)

CLI: `mcpctl get agent` table view gains KIND and STATUS columns
mirroring the `get llm` shape from v1. Public agents render as
`public/active` (the AgentRow defaults) and virtual ones surface their
true lifecycle state, so `mcpctl get agent` becomes a single-pane view
for both manually-created and mcplocal-published personas.

Smoke: tests/smoke/virtual-agent.smoke.test.ts mirrors virtual-llm's
in-process registrar pattern — publishes a fake provider + agent in
one round-trip, confirms mcpd surfaces the agent kind=virtual /
status=active under /api/v1/agents, then disconnects and verifies the
paired Llm-and-Agent both flip to inactive (deletion is GC-driven, not
disconnect-driven, so the rows must still exist post-stop). Heartbeat-
stale and 4 h sweep paths are covered by the unit suite to keep smoke
duration in check.

Docs: docs/virtual-llms.md gets a "Virtual agents (v3)" section with a
config sample, lifecycle notes, listing example, and the cluster-wide
name-uniqueness caveat. The API surface block now mentions the new
`agents[]` field on _provider-register, the join-by-session heartbeat
behavior, and the `GET /api/v1/agents` lifecycle fields. docs/agents.md
gains a one-paragraph note pointing to the v3 publishing path.

Tests: full smoke suite 141/141 (was 139, +2 new), unit suites
unchanged (mcpd 860/860, mcplocal 723/723).

src/cli/src/commands/get.ts

@@ -155,10 +155,17 @@ interface AgentRow {
   description: string;
   llm: { id: string; name: string };
   project: { id: string; name: string } | null;
+  // v3: lifecycle fields. Public agents have kind=public/status=active and
+  // these never change — virtuals get them set/updated by mcpd's
+  // AgentService as the publishing mcplocal heartbeats and disconnects.
+  kind?: 'public' | 'virtual';
+  status?: 'active' | 'inactive';
 }
 
 const agentColumns: Column<AgentRow>[] = [
   { header: 'NAME', key: 'name' },
+  { header: 'KIND', key: (r) => r.kind ?? 'public', width: 8 },
+  { header: 'STATUS', key: (r) => r.status ?? 'active', width: 10 },
   { header: 'LLM', key: (r) => r.llm.name, width: 24 },
   { header: 'PROJECT', key: (r) => r.project?.name ?? '-', width: 20 },
   { header: 'DESCRIPTION', key: (r) => truncate(r.description, 50) || '-', width: 50 },