Add native literal substring query predicates

Implement checked containsInsensitive string predicates in GraphQL, protobuf,
native SQL and bounded residual evaluation. ASCII folding is deterministic;
SQL pattern characters remain literal. Retain deferred full-text index design.

Studio migration awaits a decision on checked native getter forwarding across
conformances; do not duplicate titles or bypass private state ownership.
Compiler and local full-stack substring-query acceptance pass.

dist/camino/schema_pb.d.ts

@@ -1333,7 +1333,11 @@ export declare enum QueryComparisonOperator {
     /**
      * @generated from enum value: QUERY_COMPARISON_OPERATOR_GTE = 7;
      */
-    GTE = 7
+    GTE = 7,
+    /**
+     * @generated from enum value: QUERY_COMPARISON_OPERATOR_CONTAINS_INSENSITIVE = 8;
+     */
+    CONTAINS_INSENSITIVE = 8
 }
 /**
  * Describes the enum camino.QueryComparisonOperator.