Preserve plain-object rejection reasons in global error handlers

[FeironoX5]

Closes #171

Fix global error normalization so plain-object promise rejection reasons are captured as readable payloads instead of "[object Object]".

PR Description

Fix error normalization for global error handlers so rejected plain objects are preserved instead of being collapsed into "[object Object]".

This PR introduces a normalized CapturedError shape and uses it across the main catcher and console catcher. For unhandledrejection, plain-object reasons are now serialized into a readable title instead of going through String(obj). For browser ErrorEvents, the catcher now also builds a more useful fallback message when the original error object is unavailable (for example, cross-origin script errors).

Changes

• Added fillCapturedError and getErrorFromErrorEvent helpers in src/utils/error.ts
• Switched Catcher internals from Error | string to normalized CapturedError
• Reused normalized error extraction in consoleCatcher
• Preserved original rawError reference for deduplication/backtrace logic
• Added tests for:
  • Error
  • DOMException
  • plain-object promise rejection reasons
  • string / null / undefined rejection reasons
  • circular objects
  • cross-origin-style ErrorEvent fallback

[neSpecc]

to we need to lowercase event.type here?

[FeironoX5]

no need, we're only subscribed to unhandledrejection events, so we can gurantee unhandledrejection type:

window.addEventListener('unhandledrejection', (event: PromiseRejectionEvent) => this.handleEvent(event));

[neSpecc]

why unknown is better than exact union type?

[FeironoX5]

it's more honest in sense that error can have any type

[neSpecc]

explain this case in comment and write a test for it

[FeironoX5]

No need in test case as it shouldn't be a possible scenario, comment addded