[Stateful Encoding] add more json fields

proto/logsstateful/stateful_encoding.proto

@@ -69,14 +69,28 @@ message StructuredLog {
   repeated DynamicValue dynamic_values = 2;
 
   // JSON structured log fields. Example:
-  // Input log: {"msg":"Evicted 1 tags","agent":"core","time":"2026-03-31","level":"INFO"}
-  // Converts to: 
-  //     json_context {"agent":"core","level":"INFO","time":"2026-03-31"}
+  // Input log: {"msg":"Evicted user tags","agent":"core","time":"2026-03-31","level":"INFO"}
+  // With schema-based encoding, converts to:
+  //     json_context_schema 44 (points to "agent,level,time" in dictionary)
+  //     json_context_values ["core", "INFO", "2026-03-31"]
   //     json_message_key "msg"
   //     pattern_id 123 (points to "Evicted {} tags")
-  //     dynamic_values [1]
-  bytes json_context = 3;
+  //     dynamic_values ["user"]
+
+  // The key of the json object to put the message back into (e.g. "msg", "message", "log")
   DynamicValue json_message_key = 4;
+
+  // Schema-based JSON context encoding: separates repeating key structure from per-log values.
+  // json_context_schema_id references a DictEntryDefine whose value is a comma-separated sorted
+  // list of JSON keys (e.g. "level,service,timestamp"). Delta-encoded across batches.
+  uint64 json_context_schema_id = 5;
+  // json_context_values contains the leaf values in the same order as the schema keys.
+  // Each value is encoded as a DynamicValue (int64 for numbers, dict_index for repeated strings).
+  // Nested objects/arrays are serialized as JSON strings.
+  repeated DynamicValue json_context_values = 6;
+
+  // Deprecated: Use json_context_schema_id and json_context_values instead.
+  bytes json_context = 3;
 }
 
 message DynamicValue {