10. Zero-Copy Token Text; Reusable Evaluation Context

• Token text. Match.Text and terminal texts were built by converting []rune (code points) or []byte back to a string. The input now keeps the source string, plus a rune-to-byte offset table in code-point mode, and token text is a substring. Inputs with invalid UTF-8 in code-point mode keep copying, so U+FFFD replacement is unchanged; stream inputs also keep copying. Trade-off: token strings keep the whole input alive, like any Go substring.
• Evaluation context. Each action and predicate allocated an evalCtx. Evaluations never nest and no reference to the context survives (function values cannot be stored in fields or variables), so one context per parser is reused.
• Effect: allocations per parse JSON 230 k → 153 k, minilang 176 k → 137 k, CSV 166 k → 131 k.