Tighten static cargo and selection context proofs

fixtures/runtime/packed-event-selection-only-context-save-slice.json

@@ -0,0 +1,45 @@
+{
+  "format_version": 1,
+  "save_slice_id": "packed-event-selection-only-context-save-slice",
+  "source": {
+    "description": "Tracked save-slice document carrying raw-save-derived selection-only company/chairman context without reconstructed rosters.",
+    "original_save_filename": "captured-selection-only-context.gms",
+    "original_save_sha256": "selection-only-context-sample-sha256",
+    "notes": [
+      "tracked as JSON save-slice document rather than raw .smp",
+      "pins the selection-only company/chairman context boundary from the fixed 0x32c8 world block"
+    ]
+  },
+  "save_slice": {
+    "file_extension_hint": "gms",
+    "container_profile_family": "rt3-105-save-container-v1",
+    "mechanism_family": "rt3-105-save-post-span-bridge-v1",
+    "mechanism_confidence": "mixed",
+    "trailer_family": "rt3-105-save-trailer-v1",
+    "bridge_family": "rt3-105-save-post-span-bridge-v1",
+    "profile": null,
+    "candidate_availability_table": null,
+    "named_locomotive_availability_table": null,
+    "locomotive_catalog": null,
+    "cargo_catalog": null,
+    "company_roster": {
+      "source_kind": "save-direct-world-block-company-selection-only",
+      "semantic_family": "scenario-selected-company-context",
+      "observed_entry_count": 0,
+      "selected_company_id": 2,
+      "entries": []
+    },
+    "chairman_profile_table": {
+      "source_kind": "save-direct-world-block-chairman-selection-only",
+      "semantic_family": "scenario-selected-chairman-context",
+      "observed_entry_count": 0,
+      "selected_chairman_profile_id": 2,
+      "entries": []
+    },
+    "special_conditions_table": null,
+    "event_runtime_collection": null,
+    "notes": [
+      "selection-only save-native company/chairman context without reconstructed raw rosters"
+    ]
+  }
+}