feat: serve OpenAPI spec at /api/v1/openapi.json

Registers a handler that serves the embedded OpenAPI 3.0 spec
(compiled into the binary via oapi-codegen) at a browseable
endpoint. Uses gen.GetSwagger() to deserialize the embedded
base64+gzip spec and returns it as JSON.

46 paths, 42 schemas — agents and humans can now introspect the
full API surface without reading Go source.

internal/httpapi/server.go

@@ -159,6 +159,7 @@ func NewHandler(ctx context.Context, pool *db.Pool, cfg config.Config) http.Hand
 	//   /api/v1/executions/{id}/logs   — streamed command output, no schema type
 	//   /api/v1/learning/timeline      — derived view, no backing schema type
 	//   /api/v1/learning/trend         — derived view, no backing schema type
+	//   /api/v1/openapi.json           — API spec (embedded in binary), self-service
 	//
 	// See .agents/dev/CONTRIBUTING.md §OpenAPI codegen for the policy.
 
@@ -296,6 +297,17 @@ func NewHandler(ctx context.Context, pool *db.Pool, cfg config.Config) http.Hand
 	r.With(combinedAuth(cfg, false)).Get("/api/v1/learning/timeline", s.serveLearningTimeline)
 	r.With(combinedAuth(cfg, false)).Get("/api/v1/learning/trend", s.serveLearningTrend)
 
+	// Serve the OpenAPI spec at a browseable endpoint (agents + humans)
+	r.Get("/api/v1/openapi.json", func(w http.ResponseWriter, req *http.Request) {
+		swagger, err := gen.GetSwagger()
+		if err != nil {
+			writeProblem(w, req, http.StatusInternalServerError, "failed to load spec", "")
+			return
+		}
+		w.Header().Set("Content-Type", "application/json")
+		json.NewEncoder(w).Encode(swagger)
+	})
+
 	// Mount MCP at /mcp (plan R3-10)
 	nomosAgentID := uuid.Nil
 	if cfg.NomosAgentID != "" {