fix: avoid concurrent modification during event dispatch

[ZGaopeng]

No description provided.

[Copilot]

Pull request overview

This PR aims to prevent ConcurrentModificationError when event handlers are added/removed during Iris event dispatch.

Changes:

• Update event dispatch to iterate over a snapshot of handlers (toList) and skip handlers removed mid-dispatch.
• Make ScopedObjects.clear() iterate over a snapshot of pool.values to avoid concurrent modification during disposal.
• Add a regression test reproducing add/remove-during-dispatch scenarios.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 6 comments.

File	Description
test/repro_concurrent_modification_test.dart	Adds a repro/regression test for handler add/remove during dispatch.
lib/src/scoped_objects.dart	Snapshots pool.values during clear() to avoid mutation while disposing.
lib/src/platform/iris_method_channel_interface.dart	Changes handler storage to copy-on-write Set updates and adjusts disposal behavior.
lib/src/iris_method_channel.dart	Uses a handler snapshot during dispatch and adds exception handling around dispatch.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 4 comments.

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