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/mcp/server.go

@@ -243,12 +243,13 @@ func newServer(pool *db.Pool, agentID uuid.UUID) *mcp.Server {
 		}
 		correlationID := uuid.New().String()
 
+		execName := action + " on " + targetSlug + " (" + id.String()[:8] + ")"
 		execSlug := "exec:" + targetSlug + ":" + id.String()[:8]
 
 		_, err = pool.Exec(ctx, `
 			INSERT INTO entities (id, slug, type, name, attributes)
 			VALUES ($1, $2, 'execution', $3, '{}')`,
-			id, execSlug, action+" on "+targetSlug)
+			id, execSlug, execName)
 		if err != nil {
 			return textResult(fmt.Sprintf("insert entity: %v", err)), nil
 		}