feat(core): add timeout fallback for change-server subscription responses

[samholmes]

If the change-server subscription response does not occur within 15 seconds, the wallet's mode switches to polling while waiting for the subscription response. When the response is received, the wallet returns to subscribed mode.

This limits the worst-case sync delay when change-server is available but unresponsive to only 15 seconds before falling back to polling.

CHANGELOG

Does this branch warrant an entry to the CHANGELOG?

• Yes
• No

Dependencies

none

Description

none

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• To see the specific tasks where the Asana app for GitHub is being used, see below:
  • https://app.asana.com/0/0/1212754123530599

---

Note

Improves resilience of change-server subscriptions by falling back to polling when responses are slow.

• Add 15s timeout (CHANGE_SERVER_SUBSCRIPTION_TIMEOUT_MS) in currency-pixie to mark pending subscriptions as subscribingSlowly, enabling polling; cleared when subscribe results return; timeout cleaned up in destroy()
• Extend ChangeServiceSubscriptionStatus with subscribingSlowly and include it in subscription status transitions and filters
• Update currency-wallet-pixie to run syncNetwork polling when status includes subscribingSlowly
• Refactor changeServiceManager to an object with update/destroy, and ensure subscription batching, status updates, and lifecycle handling respect the new fallback path
• Update CHANGELOG.md with the new behavior

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