feat: support durable task cancellation without foreign keys

protocol/workerv1/worker.schema.json

@@ -115,6 +115,9 @@
           "type": "integer",
           "minimum": 1,
           "maximum": 256
+        },
+        "cancellation_notifications": {
+          "type": "boolean"
         }
       },
       "required": [
@@ -184,7 +187,8 @@
           "enum": [
             "SUCCEEDED",
             "FAILED",
-            "UNKNOWN"
+            "UNKNOWN",
+            "CANCELLED"
           ]
         },
         "result": {
@@ -242,7 +246,8 @@
               "outcome": {
                 "enum": [
                   "SUCCEEDED",
-                  "UNKNOWN"
+                  "UNKNOWN",
+                  "CANCELLED"
                 ]
               }
             }
@@ -305,6 +310,9 @@
         },
         "server_time": {
           "$ref": "#/$defs/time"
+        },
+        "cancel_requested_at": {
+          "$ref": "#/$defs/time"
         }
       },
       "required": [
@@ -920,8 +928,63 @@
         },
         {
           "$ref": "#/$defs/errorFrame"
+        },
+        {
+          "$ref": "#/$defs/cancellationFrame"
         }
       ]
+    },
+    "cancellation": {
+      "type": "object",
+      "properties": {
+        "task_id": {
+          "$ref": "#/$defs/id"
+        },
+        "attempt_id": {
+          "$ref": "#/$defs/id"
+        },
+        "epoch": {
+          "$ref": "#/$defs/uint64"
+        },
+        "requested_at": {
+          "$ref": "#/$defs/time"
+        }
+      },
+      "required": [
+        "task_id",
+        "attempt_id",
+        "epoch",
+        "requested_at"
+      ],
+      "additionalProperties": false
+    },
+    "cancellationFrame": {
+      "type": "object",
+      "properties": {
+        "protocol_version": {
+          "const": "1"
+        },
+        "type": {
+          "const": "task.cancel"
+        },
+        "message_id": {
+          "$ref": "#/$defs/id"
+        },
+        "session_id": {
+          "$ref": "#/$defs/id"
+        },
+        "body": {
+          "$ref": "#/$defs/cancellation"
+        }
+      },
+      "required": [
+        "protocol_version",
+        "type",
+        "message_id",
+        "session_id",
+        "body"
+      ],
+      "additionalProperties": false
     }
   }
 }