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(