Filter Copilot sessions by local data

[roblourens]

This change filters Copilot SDK sessions to only list sessions that already have Agent Host session data. That keeps sessions created by other Copilot CLI agents out of the Agents window without creating per-session databases during listing.

Summary:

• Gate CopilotAgent.listSessions results on an existing session database via tryOpenDatabase.
• Defer project resolution and project metadata writes until after the ownership/database-existence gate.
• Add focused unit coverage with a fake Copilot client and real in-memory SessionDatabase instances.

Validation:

• Diagnostics clean.
• CopilotAgent tests passed: 9/9.
• Hygiene passed on the changed files with only the existing TypeScript-version warning.
• Council review: no blocking issues found from two reviewers.

(Written by Copilot)

[Copilot]

Pull request overview

Filters Copilot SDK session listing in the agent host so that only sessions with existing local Agent Host session data (session DB) appear in the Agents window, avoiding side effects (DB creation / project metadata writes) during session enumeration.

Changes:

• Gate CopilotAgent.listSessions() on an existing session database via ISessionDataService.tryOpenDatabase() (and only then resolve/store project info).
• Introduce an injectable ICopilotClient surface + factory hook to enable fakes in unit tests.
• Add focused unit tests using a fake Copilot client and in-memory SessionDatabase instances to verify ownership filtering and metadata reads.

Show a summary per file

File	Description
src/vs/platform/agentHost/node/copilot/copilotAgent.ts	Adds injectable Copilot client surface and filters session listing to only sessions with existing DB-backed metadata.
src/vs/platform/agentHost/test/node/copilotAgent.test.ts	Adds unit coverage validating session filtering by DB existence and metadata read behavior without DB creation.

Copilot's findings

• Files reviewed: 2/2 changed files
• Comments generated: 1