Unify agentHost server-side dispatch: remove IProtocolSideEffectHandler

[roblourens]

Eliminate the IProtocolSideEffectHandler interface and make ProtocolServerHandler talk to IAgentService directly. This removes the duplicate adapter layer between the WebSocket protocol server and the real service implementation.

Problem

There were two different server-side dispatch layers for the same operations, both ending up at AgentService:

1. IPC MessagePort path (local): ProxyChannel auto-serializes IAgentService method calls
2. WebSocket JSON-RPC path (remote/CLI): ProtocolServerHandler → IProtocolSideEffectHandler → manual adapter → AgentService

The IProtocolSideEffectHandler interface duplicated IAgentService with different method signatures, required a ~40-line inline adapter in agentHostMain.ts, and the standalone server (agentHostServerMain.ts) manually wired SessionStateManager + AgentSideEffects instead of using AgentService.

Changes

• ProtocolServerHandler now takes IAgentService + SessionStateManager + IProtocolServerConfig instead of IProtocolSideEffectHandler
• Deleted the IProtocolSideEffectHandler interface entirely
• Deleted the ~40-line inline adapter in agentHostMain.ts
• agentHostServerMain.ts now creates AgentService instead of manually wiring SessionStateManager + AgentSideEffects
• Removed implements IProtocolSideEffectHandler from AgentSideEffects
• Removed 6 dead methods from AgentSideEffects that were only needed by the deleted interface (handleCreateSession, handleDisposeSession, handleListSessions, handleGetResourceMetadata, handleAuthenticate, getDefaultDirectory)
• Type conversions (URI↔string, IAgentSessionMetadata↔ISessionSummary) now happen at the protocol boundary in ProtocolServerHandler
• Fixed dispatchAction double-dispatch: WS path previously dispatched to stateManager AND called handleAction (which dispatched to stateManager again)
• Extension methods (getResourceMetadata, authenticate, etc.) now call IAgentService directly instead of untyped fallbacks
• authenticate params are now validated with proper JSON-RPC error code (-32602)

(Written by Copilot)

[Copilot]

Pull request overview

This PR removes the extra server-side adapter layer (IProtocolSideEffectHandler) and routes WebSocket JSON-RPC requests directly to IAgentService, aligning the WebSocket and IPC dispatch paths and simplifying the standalone agent host server wiring.

Changes:

• Refactors ProtocolServerHandler to depend on IAgentService (plus config) and removes IProtocolSideEffectHandler.
• Updates the standalone server (agentHostServerMain.ts) to construct and use AgentService directly.
• Updates unit tests and protocol documentation to reflect the new dispatch boundary and protocol validation.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/vs/platform/agentHost/test/node/protocolServerHandler.test.ts	Reworks mocks/tests to target IAgentService instead of the removed side-effect handler interface.
src/vs/platform/agentHost/test/node/agentSideEffects.test.ts	Removes tests for side-effect handler methods that were deleted along with IProtocolSideEffectHandler.
src/vs/platform/agentHost/protocol.md	Updates contributor checklist to reflect the new handler/service boundary.
src/vs/platform/agentHost/node/protocolServerHandler.ts	Main refactor: dispatches protocol operations to IAgentService, adds config, removes IProtocolSideEffectHandler, fixes double-dispatch.
src/vs/platform/agentHost/node/agentSideEffects.ts	Drops implements IProtocolSideEffectHandler and deletes side-effect methods that were only needed for that interface.
src/vs/platform/agentHost/node/agentHostServerMain.ts	Simplifies standalone server wiring to create AgentService and pass it to ProtocolServerHandler.
src/vs/platform/agentHost/node/agentHostMain.ts	Removes the inline adapter and wires ProtocolServerHandler directly to AgentService.