BridgeJS: Enforce throws(JSException) on @JS protocol methods

[krodak]

Overview

• Require throws(JSException) on @JS protocol methods, matching the import side (@JSFunction) behavior
• Fix generated protocol wrapper code to propagate throws effect
• Updated tests and documentation

Test updates

• Protocol.swift test input: Added throws(JSException) to all protocol methods
• ExportAPITests.swift: Updated DataProcessor protocol methods with throws
• Regenerated snapshots

Documentation

• Updated Exporting-Swift-Protocols.md with throws requirement and examples

Motivation

This partially addresses the inconsistency where @JSFunction (import side) requires throws(JSException) but @JS protocol methods (export side) didn't.

Properties will be covered in separate PR 🙏🏻

[kateinoigakukun]

Thanks!

[kateinoigakukun]

I think we need to enable the exception check emitted by CallJSEmission (or it needs to be done after the property interface adjustment?)

[krodak]

@kateinoigakukun my bad, now added exception checking for protocol wrapper methods with new BridgeContext.exportSwiftProtocol case.

The issue was that protocol wrappers call into JavaScript (like .importTS), so they indeed need exception checking that I missed. But they also need to support Swift heap objects as parameters/returns (like .exportSwift), hence new type 🙏🏻
For now this only applies to methods. Property accessors will be updated in a follow-up PR.

[kateinoigakukun]

Could you remove this snapshot file? It's now moved under BridgeJSCodegenTests.