chore: updated deprecation notices and fixed types

[lwin-kyaw]

Motivation and Context

Jira Link:

Description

fix: Remove deprecation notices and fix type compatibility in JRPC types

Summary

• Removed premature @deprecated annotations from V1 API types, classes, and functions that are still actively used across the codebase (BasePostMessageStream, PostMessageStream, isValidStreamMessage, SerializableError, Payload, ExtendedJsonRpcRequest).
• Relocated ProviderEvents and SafeEventEmitterProvider from jrpcEngine.ts to safeEventEmitter.ts to co-locate them with the base class they extend and removed their deprecation notices.
• Fixed type compatibility error in MiddlewareScaffold — scaffold handlers with narrowed request params (e.g. JRPCRequest<{ foo: string }>) were not assignable to the previous generic type. The fix removes the Context generic from MiddlewareScaffold, drops the intermediate ScaffoldMiddlewareHandler type, and uses a never-parameter function signature so that any handler with arbitrarily-narrowed params remains assignable.
• Relaxed JRPCRequest<Params> generic from Params extends JRPCParams to Params = JRPCParams to allow non-JRPCParams types (e.g. { foo: string }) as request parameters.
• Fixed frozen object mutation in PostMessageStream._postMessage — the data object is now shallow-copied before mutation to avoid errors when the incoming object is frozen.

Changed Files

File	Change
src/jrpc/basePostMessageStream.ts	Removed @deprecated from isValidStreamMessage and BasePostMessageStream
src/jrpc/interfaces.ts	Removed @deprecated from Payload and ExtendedJsonRpcRequest; relaxed JRPCRequest generic constraint
src/jrpc/jrpcEngine.ts	Moved ProviderEvents and SafeEventEmitterProvider out; updated imports
src/jrpc/safeEventEmitter.ts	Added ProviderEvents type and SafeEventEmitterProvider interface
src/jrpc/index.ts	Re-exported ProviderEvents and SafeEventEmitterProvider from new location
src/jrpc/serializableError.ts	Removed @deprecated from SerializableError
src/jrpc/postMessageStream.ts	Removed @deprecated from PostMessageStream; shallow-copy data before mutation
src/jrpc/v2/v2interfaces.ts	Removed ScaffoldMiddlewareHandler; simplified MiddlewareScaffold type
src/jrpc/v2/createScaffoldMiddleware.ts	Removed Context generic from MiddlewareScaffold usage; added type cast for handler
src/jrpc/v2/providerUtils.ts	Updated imports to use safeEventEmitter instead of jrpcEngine
test/v2/createScaffoldMiddleware.test.ts	Added test for scaffold handler with narrowed request params

Test Plan

• Existing scaffold middleware tests pass
• New test case validates that a handler with narrowed params (JRPCRequest<{ foo: string }>) works correctly at runtime
• Verify no downstream type errors in consuming packages

How has this been tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project. (run lint)
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.
• My code requires a db migration.

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Note

Medium Risk
Mostly type- and export-level changes, but they affect public JRPC provider/scaffold typing and add a runtime tweak to PostMessageStream message handling that could impact cross-window messaging behavior.

Overview
Removes several premature @deprecated annotations from still-used JRPC V1 APIs (stream utilities, request types, and SerializableError).

Moves ProviderEvents and SafeEventEmitterProvider type definitions into safeEventEmitter.ts and updates exports/imports so both V1 and V2 provider utilities reference the shared definitions.

Fixes V2 scaffold typing by simplifying MiddlewareScaffold (dropping the context generic and using a never-arg function signature) and updating createScaffoldMiddleware accordingly; adds a test ensuring handlers with narrowed JRPCRequest params type-check and run.

Hardens PostMessageStream._postMessage by shallow-copying object payloads before mutating _origin, avoiding crashes when the input object is frozen.

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