feat(core-dsr): Payload impls, recording doubles, DI binders, contract tests

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

coverage/summary.json

@@ -1,18 +1,18 @@
 {
-  "generatedAt": "2026-05-19T19:30:03.273Z",
-  "commit": "86d9492",
+  "generatedAt": "2026-05-19T19:59:56.279Z",
+  "commit": "8068d1b",
   "repo": {
-    "statements": 96.74,
-    "branches": 92.15,
-    "functions": 96.92,
-    "lines": 96.74,
+    "statements": 97.04,
+    "branches": 92.09,
+    "functions": 96.87,
+    "lines": 97.04,
     "counts": {
-      "lf": 4632,
-      "lh": 4481,
-      "brf": 917,
-      "brh": 845,
-      "fnf": 292,
-      "fnh": 283
+      "lf": 5107,
+      "lh": 4956,
+      "brf": 1012,
+      "brh": 932,
+      "fnf": 319,
+      "fnh": 309
     }
   },
   "byPackage": {
@@ -74,16 +74,16 @@
     },
     "@repo/core-dsr": {
       "statements": 100,
-      "branches": 100,
-      "functions": 100,
+      "branches": 92,
+      "functions": 96.88,
       "lines": 100,
       "counts": {
-        "lf": 0,
-        "lh": 0,
-        "brf": 5,
-        "brh": 5,
-        "fnf": 5,
-        "fnh": 5
+        "lf": 475,
+        "lh": 475,
+        "brf": 100,
+        "brh": 92,
+        "fnf": 32,
+        "fnh": 31
       }
     },
     "@repo/core-shared": {