fix: parse MCP result payloads and drop place idempotency_key

Typed result structs replace empty envelopes. Equity place sends
ref_id only so live additionalProperties:false schemas accept the call.

scanner/scanner.go

@@ -42,14 +42,29 @@ type Column struct {
 // FilterSpecsRequest is the argument set for get_scanner_filter_specs (none).
 type FilterSpecsRequest struct{}
 
+// FilterSpec is one filter type from get_scanner_filter_specs.
+type FilterSpec struct {
+	FilterType string `json:"filter_type"`
+	Name       string `json:"name"`
+}
+
 // FilterSpecsResult is the parsed get_scanner_filter_specs payload.
-type FilterSpecsResult struct{}
+type FilterSpecsResult struct {
+	Specs []FilterSpec
+}
 
 // DatapointsRequest is the argument set for get_scanner_datapoints (none).
 type DatapointsRequest struct{}
 
+// Datapoint is one expression token from get_scanner_datapoints.
+type Datapoint struct {
+	Name string `json:"name"`
+}
+
 // DatapointsResult is the parsed get_scanner_datapoints payload.
-type DatapointsResult struct{}
+type DatapointsResult struct {
+	Datapoints []Datapoint
+}
 
 // ScansRequest is the argument set for get_scans (none).
 type ScansRequest struct{}
@@ -74,8 +89,24 @@ type CreateRequest struct {
 	Title   string
 }
 
+// ScanResult is a saved scan plus optional live rows.
+type ScanResult struct {
+	ID    string
+	Title string
+	Rows  []ScanRow
+	Total int
+}
+
+// ScanRow is one live scanner match.
+type ScanRow struct {
+	Symbol       string
+	InstrumentID string
+}
+
 // CreateResult is the parsed create_scan payload.
-type CreateResult struct{}
+type CreateResult struct {
+	ScanResult
+}
 
 // PreviewRequest is the argument set for preview_scan.
 type PreviewRequest struct {
@@ -84,7 +115,9 @@ type PreviewRequest struct {
 }
 
 // PreviewResult is the parsed preview_scan payload.
-type PreviewResult struct{}
+type PreviewResult struct {
+	ScanResult
+}
 
 // RunRequest is the argument set for run_scan.
 type RunRequest struct {
@@ -92,7 +125,9 @@ type RunRequest struct {
 }
 
 // RunResult is the parsed run_scan payload.
-type RunResult struct{}
+type RunResult struct {
+	ScanResult
+}
 
 // UpdateFiltersRequest is the argument set for update_scan_filters.
 type UpdateFiltersRequest struct {
@@ -101,7 +136,9 @@ type UpdateFiltersRequest struct {
 }
 
 // UpdateFiltersResult is the parsed update_scan_filters payload.
-type UpdateFiltersResult struct{}
+type UpdateFiltersResult struct {
+	ScanResult
+}
 
 // UpdateConfigRequest is the argument set for update_scan_config.
 type UpdateConfigRequest struct {
@@ -112,7 +149,9 @@ type UpdateConfigRequest struct {
 }
 
 // UpdateConfigResult is the parsed update_scan_config payload.
-type UpdateConfigResult struct{}
+type UpdateConfigResult struct {
+	ScanResult
+}
 
 // FilterSpecs calls get_scanner_filter_specs.
 func (c *Client) FilterSpecs(ctx context.Context, req FilterSpecsRequest) (FilterSpecsResult, error) {