raposza/tools: platform/caql-core/README.md

<!-- Copyright (c) 2026 bentzn --> <!-- SPDX-License-Identifier: Apache-2.0 --> # caql-core CaQL parser, AST and semantics. A language, not a tool. S-2: syntax and AST are major-version neutral; version-specific validation happens after parse, never in the grammar. S-3: **only scalar things bind, an