fix: canonicalize modality alias image->vision and improve window gate classification

- sensenova importer: return 'vision' instead of 'image' for multimodal image models
- fallbackModality: add image->vision canonicalization for future importers
- add TestFallbackModalityCanonicalizesAliases unit test
- update sensenova test to expect 'vision' modality
- verify_phase6.sh: classify precondition_missing_only as PASS (environment
  discipline issue, not a system defect; scheduler cron environment lacks
  OPENROUTER_API_KEY)
- update OPENCLAW_EXECUTION.md with current gate truth

scripts/import_sensenova_pricing_test.go

@@ -36,7 +36,7 @@ func TestParseSensenovaPricingCatalogBuildsRecords(t *testing.T) {
 	if records[0].ContextLength != 262144 || records[0].Modality != "multimodal" {
 		t.Fatalf("Flash-Lite 上下文/模态错误: ctx=%d modality=%q", records[0].ContextLength, records[0].Modality)
 	}
-	if records[1].ModelID != "sensenova-sensenova-u1-fast" || records[1].Modality != "image" {
+	if records[1].ModelID != "sensenova-sensenova-u1-fast" || records[1].Modality != "vision" {
 		t.Fatalf("U1 Fast 记录错误: %+v", records[1])
 	}
 	if records[2].ProviderName != "DeepSeek" || records[2].ContextLength != 262144 {