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.

src/query/relational-compile.ts

@@ -53,7 +53,7 @@ const pairs = (node: ValueNode): readonly import("graphql").ObjectFieldNode[] =>
   node.kind === "ObjectValue"
     ? node.fields
     : fail("QUERY_UNSUPPORTED_FEATURE", "Query structure must be a literal object", node);
-const ops = new Set(["eq", "in", "isNull", "lt", "lte", "gt", "gte"]);
+const ops = new Set(["eq", "containsInsensitive", "in", "isNull", "lt", "lte", "gt", "gte"]);
 const prefix = (a: readonly string[], b: readonly string[]) => a.every((part, i) => part === b[i]);
 
 export function relationalCompiler(

src/query/relational-proto.ts

@@ -66,6 +66,7 @@ export function relationalWire(
               value: argument(p.value),
               operator: {
                 eq: wire.QueryComparisonOperator.EQ,
+                containsInsensitive: wire.QueryComparisonOperator.CONTAINS_INSENSITIVE,
                 in: wire.QueryComparisonOperator.IN,
                 isNull: wire.QueryComparisonOperator.IS_NULL,
                 lt: wire.QueryComparisonOperator.LT,

src/query/relational.ts

@@ -65,7 +65,7 @@ export type QueryPredicate =
   | {
       kind: "compare";
       expression: QueryExpression;
-      operator: "eq" | "in" | "isNull" | "lt" | "lte" | "gt" | "gte";
+      operator: "eq" | "containsInsensitive" | "in" | "isNull" | "lt" | "lte" | "gt" | "gte";
       value: QueryArgument;
     }
   | {
@@ -93,7 +93,7 @@ export type QueryAggregatePredicate =
   | {
       kind: "compare";
       expression: QueryExpression | QueryReduction;
-      operator: "eq" | "in" | "isNull" | "lt" | "lte" | "gt" | "gte";
+      operator: "eq" | "containsInsensitive" | "in" | "isNull" | "lt" | "lte" | "gt" | "gte";
       value: QueryArgument;
     };
 export interface QueryKey {

src/query/schema.ts

@@ -139,6 +139,7 @@ export function querySchema(
     let result = comparisons.get(key);
     if (!result) {
       const fields: GraphQLInputFieldConfigMap = { eq: { type: value }, isNull: { type: GraphQLBoolean } };
+      if (base.kind === "scalar" && base.name === "string") fields.containsInsensitive = { type: value };
       if (base.kind === "scalar" && base.name !== "bytes")
         fields.in = { type: new GraphQLList(new GraphQLNonNull(value)) };
       if (base.kind === "scalar" && base.name !== "bool" && base.name !== "bytes")