feat: add error strategy option to batch resolver

[JaysonGCS]

Description

Adds a configurable errorStrategy to the batch resolver so callers can choose how errors propagate across a batch. Previously, any error from the batch resolver was always broadcast to every caller in the batch, meaning a single failing item could reject unrelated callers.

Changes Made

• Added an errorStrategy option ('broadcast' | 'isolate') to BatchOptions.
• broadcast (default): preserves existing behaviour — a resolver error rejects all callers in the batch.
• isolate: the batch resolver returns per-item promises (Promise<TReturnType>[]), so each caller settles independently. Failed or cancelled callers bail immediately without affecting the rest of the batch.
• Updated batchResolver to accept both AsyncBatchFunction and the new AsyncIsolateBatchFunction signature.
• Updated the interception logic to handle per-item settlement, including releaseWithError per item and correct _activeBatchCount accounting; synchronous throws from the resolver still broadcast.
• Added types/constants for the new strategy.
• Added tests in src/index.test.ts covering isolate vs broadcast behaviour.
• Updated README.md documentation and the examples/webapp demo (api client, config panel, defaults) to exercise the new option.

Definition of Done

• All automated tests have passed successfully.
• All manual tests have passed successfully.
• Code has been reviewed by at least one other team member.
• Code has been properly documented and commented as needed.
• All new and existing code adheres to our project's coding standards.
• All dependencies have been added or removed from the project's README or other documentation as needed.
• Any relevant documentation or help files have been updated to reflect the changes made in this pull request.
• Any necessary database migrations have been run.
• Any relevant UI changes have been reviewed and approved by the UI/UX team.

Additional Notes

Default behaviour is unchanged (broadcast), so this is a backwards-compatible, additive feature.

[github-actions]

🎉 This PR is included in version 1.2.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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