fix(polling): no-operations sync response caused hot spin that ignored abort

[nezumi0627]

Summary

Polling._listenTalkEvents (the deprecated but still exported polling generator) busy-looped whenever a sync response arrived without operationResponse.operations, which happens routinely (e.g. full-sync-only responses):

if (!(response.operationResponse && response.operationResponse.operations)) {
    continue; // skips sleep AND the AbortSignal check
}

The continue jumped back to while (true) without executing await sleep(pollingInterval) or if (signal?.aborted) break. Consequences:

• talk.sync was hammered as fast as the event loop allowed (rate-limit / ban risk),
• an AbortSignal could never stop the loop, because abort is only checked after the sleep.

Fix

Replace the early continue with a positive condition around the operations loop so every iteration falls through to the shared sleep/abort tail.

Testing

New mod.test.ts: stubs talk.sync to resolve {} (no operations), polls with a 50 ms interval, aborts after 150 ms. Asserts the poll count stays bounded and the loop actually terminates. On the old code this test never completes — the abort is ignored and syncCalls explodes.

Full suite: deno test --allow-all passes.