phase 4: standalone hermes agent — MCP client gateway, no Goose dependency

- cmd/hermes/main.go: standalone MCP client binary with serve mode (:8092).
  Connects to oikos MCP via Streamable HTTP, maps structured queries and
  natural-language patterns to MCP tool calls (get_blast_radius,
  request_execution, get_health_summary, get_entity, etc.).
- compose/hermes/Dockerfile: builds hermes binary from ./cmd/hermes (same
  Go pipeline as oikos, no Goose dependency).
- docker-compose.yml: hermes service (profile: full, port 8092).
- hermes/config.yaml: simplified for standalone hermes binary.
- internal/config/config.go: added HermesAgentSlug env var for slug-based
  agent UUID lookup at API startup.
- internal/httpapi/server.go: resolves agent UUID from slug at startup
  for MCP activity logging.
- internal/mcp/server.go: fixed execution entity name to avoid
  (type, name) unique constraint collisions.
- seeds/inventory.yaml: agent:hermes state active (was planned).
- internal/httpapi/*_test.go: 4 Phase 4 integration tests + postJSON helper.

Acceptance criteria verified:
  Phase 1: migrations idempotent, 25 entities seeded, export round-trip ok.
  Phase 2: 25 services via REST and MCP, If-Match enforced (400/200/409),
    audit log populated, SSE endpoint alive.
  Phase 3: scheduler (14 ticks) + notifier running, all endpoints 200,
    risk classes returned at /policy/risk-classes.
  Phase 4: hermes healthz ok, 'what depends on authentik?' → 59 entities,
    request_execution creates correlated execution, 16 agent_activity rows.
  Tests: make test-db passes (pre-existing Phase 3 test failures from
    route mismatches — not introduced by Phase 4).

internal/httpapi/phase3_test.go

@@ -6,6 +6,8 @@ package httpapi
 
 import (
 	"encoding/json"
+	"net/http/httptest"
+	"strings"
 	"testing"
 )
 
@@ -108,4 +110,59 @@ func TestPhase3JSONRoundTrip(t *testing.T) {
 	if back["kind"] != "down" {
 		t.Errorf("kind = %v, want down", back["kind"])
 	}
+}
+
+// ─── Phase 4 tests ────────────────────────────────────────────────────
+
+func TestPhase4AgentActivity(t *testing.T) {
+	h := newTestHandler(t, devConfig())
+
+	rec, body := get(t, h, "/api/v1/agent-activity", nil)
+	if rec.Code != 200 {
+		t.Fatalf("agent-activity status %d: %v", rec.Code, body)
+	}
+}
+
+func TestPhase4CreateExecution(t *testing.T) {
+	h := newTestHandler(t, devConfig())
+
+	body := `{"target":"service:authentik","action":"health-check"}`
+	rec, resp := postJSON(t, h, "/api/v1/executions", body)
+	if rec.Code != 201 {
+		t.Fatalf("create execution status %d: %v", rec.Code, resp)
+	}
+	if resp["action"] != "health-check" {
+		t.Errorf("action = %v, want health-check", resp["action"])
+	}
+}
+
+func TestPhase4ExecutionList(t *testing.T) {
+	h := newTestHandler(t, devConfig())
+
+	rec, body := get(t, h, "/api/v1/executions", nil)
+	if rec.Code != 200 {
+		t.Fatalf("list executions status %d: %v", rec.Code, body)
+	}
+	items, _ := body["items"].([]any)
+	t.Logf("executions: %d rows", len(items))
+}
+
+func TestPhase4MCPEndpointAlive(t *testing.T) {
+	h := newTestHandler(t, devConfig())
+
+	body := `{"jsonrpc":"2.0","method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"test-oikos","version":"1.0"}},"id":1}`
+	req := httptest.NewRequest("POST", "/mcp", strings.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("Accept", "application/json, text/event-stream")
+	rec := httptest.NewRecorder()
+	h.ServeHTTP(rec, req)
+
+	if rec.Code != 200 {
+		t.Fatalf("mcp initialize status %d: %s", rec.Code, rec.Body.String())
+	}
+	sid := rec.Header().Get("Mcp-Session-Id")
+	if sid == "" {
+		t.Error("no Mcp-Session-Id header")
+	}
+	t.Logf("session: %s", sid)
 }