Configurable per-call :heartbeat

[ismasan]

Per-stream heartbeat override

The #stream method also accepts a heartbeat: keyword that overrides the constructor-level setting for a single call. This is useful when a dispatcher is generally configured with a heartbeat but a particular response doesn't need one (e.g. a one-shot update, or multiple updates that don't keep the connection open for long). The previous value is restored once the call returns.

datastar = Datastar.new(request:, response:) # default heartbeat

# Disable heartbeat for this single response
datastar.stream(heartbeat: false) do |sse|
  sse.patch_elements(html)
  sse.patch_signals(progress: 100)
end

The one-shot helpers (#patch_elements, #remove_elements, #patch_signals, #remove_signals, #execute_script, #redirect) use this internally to avoid spawning a heartbeat thread for a single message.

This change is an optimisation aimed mostly at libraries using this SDK. No-heartbeat streams were possible before but not exposed in the public API.