#2539 fix(parser): make reset() safe inside callbacks

Two fixes for reset() being called from inside a callback:

• count chunks before invoking tokenizer callbacks: writeIndex is incremented before the tokenizer runs, so a reset() from a callback does not leave the chunk count one behind.
• stop closing a stack reset by a callback: the implied-close loop in onclosetag is bounded by the matched element's position, so a reset() from an onclosetag callback ends the loop instead of closing elements of the new document.

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Summary by CodeRabbit

• Bug Fixes
  • Fixed parser behavior when parsing is reset from a callback. Text queued after a reset is delivered in order, including when parsing pauses and resumes. Resetting during a closing-tag callback now stops additional closing-tag callbacks for the current input, preventing callbacks from continuing after parsing has been reset.