refactor: track-change use ZenObservable over RxJS

[daniel-graham-amplitude]

Summary

• Refactor "track-change.ts" to use Zen over RxJS

Checklist

• Does your PR title have the correct title format?
• Does your PR have a breaking change?: No

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Note

Replaces RxJS-based change tracking with ZenObservable + multicast, updates types/subscriptions, and exports Unsubscribable; test page config toggled.

• Autocapture (browser):
  • Replace RxJS fromEvent(...).pipe(...) change tracking with Zen Observable via multicast(new ZenObservable(...)) using getGlobalScope for DOM listeners in autocapture-plugin.ts.
  • Update AllWindowObservables.ChangeObservable to ZenObservable and subscriptions to Unsubscribable.
  • Refactor track-change.ts to use Zen Observable methods (filter, map) instead of RxJS operators.
• Core (analytics-core):
  • Export Unsubscribable from utils/observable and re-export in index.ts.
• Test server:
  • Toggle config: fetchRemoteConfig disabled; enable autocapture.elementInteractions in element-interactions.html.

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[daniel-graham-amplitude]

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[Copilot]

Pull Request Overview

This PR migrates the change event observable from RxJS to Zen Observable implementation to align with the project's move away from RxJS dependencies for change event tracking.

• Replaced RxJS fromEvent with manual ZenObservable implementation for change events
• Converted RxJS pipe-based operators (.pipe(filter(), map())) to ZenObservable instance methods (.filter().map())
• Updated type definitions to use ZenObservable instead of RxJS Observable for change events
• Exported Unsubscribable type from analytics-core to support the migration

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
test-server/autocapture/element-interactions.html	Enabled element interactions and disabled remote config for testing
packages/plugin-autocapture-browser/src/autocapture/track-change.ts	Migrated from RxJS pipe operators to ZenObservable instance methods
packages/plugin-autocapture-browser/src/autocapture-plugin.ts	Replaced RxJS fromEvent with manual ZenObservable implementation for change events and updated type definitions
packages/analytics-core/src/utils/observable.ts	Exported Unsubscribable type
packages/analytics-core/src/index.ts	Added Unsubscribable to public exports

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[Mercy811]

LGTM!