agentHost: sync workspace folders for existing sessions

[DonJayamanne]

Summary

• synchronize existing Editor Window Agent Host sessions when multi-root workspace folders are added or removed
• preserve the immutable primary directory and apply provider changes before confirming AHP state
• update Claude through safe query rebuilds and Codex through same-thread turn/start workspace roots
• support Remote Development URI mapping and current-folder reconciliation before prompts

Guardrails

• limited to Editor Window sessions
• excludes workspace-less, worktree-isolated, and multi-chat sessions
• Copilot dynamic mutation remains disabled until its SDK exposes an accessible-roots API
• reconciliation failures block the prompt instead of starting with stale access

Validation

• all changed unit-test files pass
• npm run typecheck-client
• npm run valid-layers-check
• hygiene checks for all changed TypeScript files
• independent code review and rubber-duck review

[Copilot]

🟡 Not ready to approve

Provisional rebinding can retry indefinitely, and one-folder or older-protocol sessions are not safely reconciled.

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Pull request overview

Adds dynamic workspace-folder synchronization for eligible Editor Window Agent Host sessions, including remote URI translation and provider-specific updates.

Changes:

• Adds awaitable AHP working-directory mutations with validation and reconciliation.
• Updates Claude and Codex sessions to apply changed secondary roots.
• Adds remote mapping and broad unit-test coverage.

File summaries

File	Description
editorRemoteAgentHostServiceClient.test.ts	Tests remote URI mapping.
agentHostWorkingDirectoryUri.ts	Converts remote working-directory URIs.
editorRemoteAgentHostServiceClient.ts	Maps remote session directories.
agentHostPty.test.ts	Updates the connection mock.
agentHostUntitledProvisionalSessionService.test.ts	Tests provisional folder changes.
agentHostSessionWorkingDirectorySynchronizer.test.ts	Tests reconciliation and trust.
agentHostNewSessionFolderService.test.ts	Tests desired-root computation.
agentHostUntitledProvisionalSessionService.ts	Recreates provisional root sets.
agentHostSessionWorkingDirectorySynchronizer.ts	Synchronizes existing sessions.
agentHostSessionHandler.ts	Reconciles roots before prompts.
agentHostNewSessionFolderService.ts	Computes stable desired root sets.
protocolServerHandler.test.ts	Tests server action forwarding.
codexPrewarmEviction.test.ts	Tests Codex root updates.
claudeAgent.test.ts	Tests Claude query rebuilding.
agentService.test.ts	Tests mutation validation and ordering.
remoteAgentHostProtocolClient.test.ts	Tests awaitable remote dispatch.
agentSubscription.test.ts	Tests optimistic action settlement.
protocolServerHandler.ts	Enables session directory actions.
codexAgent.ts	Applies roots to subsequent turns.
claudeAgentSession.ts	Rebuilds queries with desired roots.
claudeAgent.ts	Tracks desired Claude roots.
agentService.ts	Validates and serializes mutations.
localAgentHostService.ts	Exposes awaitable local dispatch.
sessionActions.ts	Exports mutation action types.
agentSubscription.ts	Adds awaitable optimistic actions.
agentService.ts (common)	Extends provider and connection APIs.
remoteAgentHostProtocolClient.ts	Dispatches and awaits action echoes.
nullAgentHostService.ts	Implements the new null-service method.

Review details

• Files reviewed: 28/28 changed files
• Comments generated: 3
• Review effort level: Balanced

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