agentHost: configure external session discovery

[Benjamin Christopher Simmonds (benibenj)]

Summary

• add chat.agentSessions.showExternal with none, all, last 24 hours, and last 7 days modes
• classify external sessions centrally in the Agent Host session registry and expose the classification through typed session metadata
• reconcile connected clients immediately while retaining live sessions, preserving legacy Copilot adoption, and forcing unused external sessions read
• keep notification baselines independent from list requests and reconcile automatically at time-window expiry
• preserve external ownership in restored live session metadata

Validation

• npm run compile
• npm run compile-client
• targeted ESLint for all changed files
• scripts\test.bat --run src\vs\platform\agentHost\test\node\agentSessionRegistry.test.ts --run src\vs\platform\agentHost\test\node\agentService.test.ts (274 passing)

Reviewer notes

The unreleased version-1 agent-host.db schema now includes is_external; existing development databases must be recreated. No migration is included by design.

Full npm run hygiene is blocked on Windows by an unrelated path-resolution error that resolves remote\package.json as C:\C:\....

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Pull request overview

Adds configurable discovery and visibility of external Agent Host sessions.

Changes:

• Adds external-session visibility modes and metadata classification.
• Persists session ownership and reconciles connected clients.
• Updates registry and service tests for external metadata.

Show a summary per file

File	Description
constants.ts	Adds the workbench setting key.
chat.shared.contribution.ts	Registers visibility mode settings.
agentSessionRegistry.test.ts	Tests ownership transitions.
agentService.test.ts	Updates expected external metadata.
agentSessionRegistry.ts	Exposes persisted ownership.
agentService.ts	Filters and reconciles external sessions.
agentHostStateManager.ts	Supports retracting surfaced sessions.
agentHostDatabase.ts	Persists external classification.
sessionState.ts	Adds typed external metadata helpers.
agentHostSchema.ts	Defines Agent Host visibility configuration.

Review details

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• Files reviewed: 10/10 changed files
• Comments generated: 4
• Review effort level: Balanced