Lazy continuation or strict marker requirement for indented lines in Markdown block quotes

Goal: Determine whether a line that begins with three spaces of indentation followed by non‑marker text inside a Markdown block quote should be interpreted as lazy continuation of the quote or as the start of a fenced code block.

Constraint: The CommonMark specification permits lazy continuation but leaves the interpretation of such a line unspecified, causing divergent behavior among parsers that either treat it as continuation or as a new code block when the line could also be seen as the opening of a fenced block.

Uncertainty: No definitive rule resolves this edge case, so authors cannot rely on consistent output across implementations without additional markers.

Should parsers treat the three‑space‑indented line as continuation of the block quote? Should they treat it as the beginning of a fenced code block? How should implementers decide which behavior to adopt for compatibility?