A runaway preview script (sync infinite loop, or a re-render loop
outpacing the bootstrap's own coalescing) had nothing detecting it -
the frame just spun. The bootstrap now heartbeats every second, and the
parent tears the iframe down if it goes _WATCHDOG_MS silent, whatever
the cause.
_coerce_tool_calls recovers a tool call guessed from `content` for
models with no native tool_calls field. That guess is weaker evidence
than the API's own structured field - a model can land on JSON shaped
like a call while only meaning to describe one - so an action tool
recovered this way now always requires approval, even under the
"allow" policy that lets a native tool_calls field run unattended.
Load Sucrase only when a JSX/TSX preview is opened, remove the hand-written transform, and leave subjective render evaluation to the reader while retaining structural fence validation.