update

Recompute the styled AnnotatedString for newCode using theme.

Branches on engine state:

• First call: equivalent to highlight — full parse + full query iteration.

• newCode == oldCode: theme-only short-circuit — re-resolves the cached captures through theme without re-parsing.

• Otherwise: tree-sitter incremental parse + scoped query over the affected byte range.

The incremental branch mutates captureSpans, oldTree, and the underlying tree-sitter Tree in several stages. Today those mutations cannot be interrupted mid-call — Parser.timeoutMicros is not exposed by the engine, so a partially updated state is unreachable in practice. If a future change exposes cancellation, the engine must be extended to roll back to its pre-call state on interrupt; that rollback contract is aspirational, not satisfied by the current implementation.

Throws