Tear down SSH tunnel when removing a remote

[roblourens]

Removing an SSH-backed agent host previously only disposed the renderer-side protocol client and SSHRelayTransport. SSHRelayTransport.dispose() removed the IPC listeners but did not tell the shared-process side to close the SSH tunnel, so the tunnel leaked and the next connect silently reused it.

Fix

Give IRemoteAgentHostService a generic ownership hook for transport-level teardown:

• Rename addSSHConnection → addManagedConnection and add an optional transportDisposable parameter. The platform service registers it on the same per-entry DisposableStore as the protocol client, so it runs on removeRemoteAgentHost, on config-driven reconciliation, and on service disposal.
• SSHRemoteAgentHostService passes a transport disposable that synchronously drops the renderer-side handle from its _connections map, fires the change event, marks the handle closed, disposes it, then best-effort tells the shared-process service to disconnect(). The early return existing branches in connect() / reconnect() are now safe across remove → reconnect because the map is cleared synchronously.
• Web and desktop tunnel renderers just pick up the rename. Their existing transports (TunnelConnectionTransport.dispose, TunnelRelayTransport.dispose) already close the underlying connection, so no behavior change there.

Tests

• New sshRemoteAgentHostService.test.ts covers the renderer lifecycle: connect registers a transport disposable, removal tears down both the renderer handle and the shared-process tunnel, reconnect after removal does not reuse the old handle, and main-process close cleans up without double-disconnecting.
• Extended remoteAgentHostService.test.ts proves the transportDisposable runs on entry removal, replacement, and service dispose.
• Full **/agentHost/**/*.test.js suite passes (714 / 1 pending / 0 failing).

(Written by Copilot)

[Copilot]

Pull request overview

This PR ensures SSH-backed remote agent host tunnels are properly torn down when a remote is removed by introducing a transport-level teardown hook owned by IRemoteAgentHostService, and wiring SSH connections to use it.

Changes:

• Renames IRemoteAgentHostService.addSSHConnection to addManagedConnection and adds an optional transportDisposable that is disposed with the entry lifecycle (remove/reconcile/service dispose).
• Updates SSH and tunnel/web-tunnel connection registration to use addManagedConnection; SSH now supplies a transport disposable that drops renderer handles and best-effort disconnects the shared-process tunnel.
• Adds/extends unit tests to validate transport teardown on removal/replacement/service disposal and SSH lifecycle behavior (remove → reconnect, main close cleanup).

Show a summary per file

File	Description
src/vs/sessions/contrib/remoteAgentHost/electron-browser/tunnelAgentHostServiceImpl.ts	Updates tunnel-backed connection registration to call addManagedConnection.
src/vs/sessions/contrib/remoteAgentHost/browser/webTunnelAgentHostService.ts	Updates web tunnel-backed connection registration to call addManagedConnection.
src/vs/sessions/contrib/remoteAgentHost/browser/remoteAgentHostActions.ts	Updates inline comment to reflect the renamed API (addManagedConnection).
src/vs/platform/agentHost/test/electron-browser/sshRemoteAgentHostService.test.ts	Adds renderer-side SSH service tests covering teardown and reconnect behavior.
src/vs/platform/agentHost/test/electron-browser/remoteAgentHostService.test.ts	Extends tests to verify transportDisposable disposal on remove/replace/service dispose.
src/vs/platform/agentHost/electron-browser/sshRemoteAgentHostServiceImpl.ts	Implements SSH transport teardown via transportDisposable and switches to addManagedConnection.
src/vs/platform/agentHost/common/remoteAgentHostService.ts	Updates service contract: rename to addManagedConnection and document transportDisposable semantics.
src/vs/platform/agentHost/browser/remoteAgentHostServiceImpl.ts	Implements addManagedConnection and ensures transport disposables are owned by per-entry stores.

Copilot's findings

• Files reviewed: 8/8 changed files
• Comments generated: 3