In default ECMAScript std::regex (no multiline flag; this parser cannot
detect construction-site flags), ^ and $ anchor to string start/end, not
line boundaries. Update RegExpCaret, RegExpDollar, and RegExpAnchor doc
comments to describe string-start/string-end semantics and note that
multiline is not modelled, mirroring PR #22200. Tokenization unchanged.
.expected files unchanged.
Bundle: github/codeql-action codeql-bundle-v2.26.1 (CodeQL CLI 2.26.1).