feat: add durable safe retries with uncertainty tracking and SDK examples

protocol/workerv1/worker.schema.json

@@ -193,6 +193,11 @@
         "error_code": {
           "type": "string",
           "maxLength": 64
+        },
+        "retryable": {
+          "type": "boolean",
+          "default": false,
+          "description": "仅 FAILED 可以为真，表示明确失败可安全重试，不表示必定安排重试。"
         }
       },
       "required": [
@@ -230,6 +235,25 @@
               }
             }
           }
+        },
+        {
+          "if": {
+            "properties": {
+              "outcome": {
+                "enum": [
+                  "SUCCEEDED",
+                  "UNKNOWN"
+                ]
+              }
+            }
+          },
+          "then": {
+            "properties": {
+              "retryable": {
+                "const": false
+              }
+            }
+          }
         }
       ]
     },
@@ -485,6 +509,10 @@
         },
         "updated_at": {
           "$ref": "#/$defs/time"
+        },
+        "effect_uncertain": {
+          "type": "boolean",
+          "description": "仍有历史执行效果未核实，重试不清除。"
         }
       },
       "required": [