feat: add session updates and message dialogs

backend/services/runtime_variables.py

@@ -210,6 +210,39 @@ class DynamicVariableStore:
             raise DynamicVariableError(f"动态变量 {name} 类型应为 {expected}")
         self.values[name] = primitive
 
+    def assign_declared_many(self, values: dict[str, Any]) -> list[str]:
+        """Atomically update public variables declared by the assistant."""
+        staged: dict[str, Primitive] = {}
+        for name, value in values.items():
+            if (
+                name.startswith(("system__", "secret__"))
+                or not VARIABLE_NAME.fullmatch(name)
+            ):
+                raise DynamicVariableError(f"会话不能更新保留变量: {name}")
+            if name not in self.variable_types:
+                raise DynamicVariableError(f"动态变量未声明: {name}")
+            primitive = _primitive(value, name)
+            expected = self.variable_types[name]
+            if not _type_matches(primitive, expected):
+                raise DynamicVariableError(f"动态变量 {name} 类型应为 {expected}")
+            staged[name] = primitive
+
+        changed = [
+            name
+            for name, value in staged.items()
+            if name not in self.values or self.values[name] != value
+        ]
+        self.values.update(staged)
+        return changed
+
+    def public_values(self) -> dict[str, Primitive]:
+        """Return the client-visible dynamic-variable snapshot."""
+        return {
+            name: value
+            for name, value in self.values.items()
+            if not name.startswith(("system__", "secret__"))
+        }
+
 
 def prepare_dynamic_config(
     cfg: AssistantConfig,