Brokk C++ grammar 0.24.3

C++ overloads following a split extern "C" closing brace now retain their preprocessor guard. C translation units can keep the C declaration while C++ translation units select the guarded overload. Closing guards also retain else/elif alternatives, including empty true branches.

The release includes the 0.24.2 fixes for conditional array bounds and namespace-qualified defaulted constructors. It tracks upstream c009222808634c1014f82438d4883753516a2c24, uses parser ABI 15, and requires Tree-sitter 0.25 or newer.

Validation covers the full grammar corpus and highlighting suite, Rust bindings on the current and minimum runtimes, Node/Python/Go/Swift bindings, C binding build, lint, and package contents.