Add timeout and cancellation

A local request can still hang or take too long.

Pass an abort signal to fetch():

const signal = AbortSignal.timeout(8000)

const response = await fetch('http://localhost:11434/api/chat', {
  method: 'POST',
  headers: { 'content-type': 'application/json' },
  body: JSON.stringify(request),
  signal,
})

Eight seconds is an example, not a universal default. Measure the real model and choose a budget that matches the feature.

Cancellation has another use. If the user closes a view or replaces the input, the old result may no longer matter. Abort the pending request so a stale answer cannot update the interface later.

Handle these outcomes separately in logs:

• user or lifecycle cancellation
• timeout
• connection failure
• HTTP error
• invalid model output

They may share the same deterministic fallback, but they need different diagnostics.