Refactor AgentService instantiation

[roblourens]

Summary

• construct AgentService through dependency injection in one strict Agent Host service scope
• expose one createAgentHostRuntime composition function that always builds the same complete shared service graph
• build the complete AgentService core and collaborator graph in agentServiceComposition.ts; AgentService has no service collection, instantiation service, services.set, createInstance, or service-class construction
• use one guarded initialization bundle for the few genuine callbacks into the fully constructed AgentService
• make the only host-specific graph choice explicit: renderer BYOK or unavailable BYOK; quiet mode no longer changes the DI graph
• register the shared authentication service directly for Git state and changeset operations
• replace the test-only AgentService clock callback with runWithFakedTimers
• delay Claude SDK environment mutation until the first SDK call so eager graph construction is inert
• keep only entry-point policy—logging, SDK overrides, provider enablement, and transports—in the two main files

Validation

• npm run typecheck-client
• npm run core-ci
• npm run valid-layers-check
• Agent Host service and provider proxy tests: 405 passing, 17 pending
• strict renderer-BYOK runtime construction test
• standalone agent host startup in quiet/mock and full provider modes
• WebSocket listener probes returned 426 Upgrade Required

(Written by Copilot)

[Copilot]

Pull request overview

Refactors AgentService construction around a dedicated child DI scope shared by host services and providers.

Changes:

• Adds an agent-host application factory and DI-backed AgentService options.
• Shares scoped services, including ICopilotApiService, across consumers.
• Updates AgentService tests to use the production construction path.

Show a summary per file

File	Description
src/vs/platform/agentHost/node/agentHostApplication.ts	Creates the application DI scope.
src/vs/platform/agentHost/node/agentService.ts	Converts AgentService to DI construction.
src/vs/platform/agentHost/node/agentHostMain.ts	Uses scoped application services.
src/vs/platform/agentHost/node/agentHostServerMain.ts	Applies the scope to standalone hosting.
src/vs/platform/agentHost/test/node/agentServiceTestUtils.ts	Adds production-style test construction.
src/vs/platform/agentHost/test/node/agentService.test.ts	Migrates AgentService tests.
src/vs/platform/agentHost/test/node/agentSideEffects.test.ts	Migrates side-effect tests.
src/vs/platform/agentHost/test/node/claudeAgent.test.ts	Migrates Claude provider coverage.

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• Files reviewed: 7/8 changed files
• Comments generated: 0
• Review effort level: Balanced