fix: diagnostics track uncaught sdk errors

[Mercy811]

Summary

https://amplitude.atlassian.net/wiki/spaces/GOV/pages/3501359165/Diagnostics+track+uncaught+SDK+errors#1.-Execution-Context-Tracking

DO NOT MERGE NOW

Let diagnostics track uncaught errors from the SDK.
#1413

Implementation:

• Maintain a global context depth tracker
  • Increase the tracker when entering the original function and decrease the tracker when exiting
  • For async functions, put error objects in a queue pendingSDKErrors
• Wrap main entry points: init() and process() with the DiagnosticsUncaughtError decorator which updates the tracker
• Add an on error event handler
  • When an error happens, check if the context tracker is greater than 0 OR if it’s in pendingSDKErrors

Test server example:

GMT20251125-010300_Clip_Diagnostics.capture.uncaught.sdk.error.mp4

Checklist

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Note

Adds execution-context tracking and global web handlers to report uncaught SDK errors to Diagnostics, applies tracking to init/process, exposes decorator, and adds tests/demo; enables decorators in TS config.

• Diagnostics (core):
  • Execution tracking: Add diagnostics-uncaught-sdk-error-global-tracker with getExecutionTracker, DiagnosticsUncaughtError decorator, and error tagging helpers.
  • Global handlers (web): Add diagnostics-uncaught-sdk-error-web-handlers to capture error and unhandledrejection and record analytics.errors.uncaught via IDiagnosticsClient.
  • Integration: Initialize error tracking in DiagnosticsClient when sampled/enabled.
  • Exports: Export DiagnosticsUncaughtError from src/index.ts.
• Browser:
  • Decorate AmplitudeBrowser._init and process with @DiagnosticsUncaughtError to mark SDK execution.
• Tests:
  • Add comprehensive unit tests for execution tracker and web handlers; update index.test.ts to validate new export.
• Demo:
  • Expand test-server/diagnostics.html to demonstrate dropped events and uncaught error capture scenarios.
• Config:
  • Enable experimentalDecorators in tsconfig.json.

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[Mercy811]

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[Mercy811]

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[Mercy811]

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[sojingle]

Overall lgtm.
There is a potential issue to note: if an external callback is called synchronously by amplitude, errors that occur during this period might be treated as amplitude errors. If this situation occurs, should we treat it as by design, or can we mark such callbacks to exclude them from being recorded?

[Mercy811]

Closing this and go with #1419 instead