Fix agent host agents in vscode (#312628)

* chat: register in-place action for programmatic chat session contributions

The autorun that registers `openNewChatSessionInPlace.<type>` actions
filters `_contributions` by `_contributionDisposables.has(...)`. Only
extension-contributed providers were getting added to that map (via
`_evaluateAvailability`), so programmatically-registered contributions
(local + remote agent hosts) had no in-place action and the session-type
picker in VS Code threw "command not found" when switching to the local
Copilot CLI agent host.

Mark programmatic registrations as active in
`registerChatSessionContribution` so they participate in the autorun.

Also disambiguate the agent-host displayName in VS Code by suffixing
"- Agent Host", since the extension-host Copilot CLI harness uses the
same "Copilot CLI" label. The Agents window keeps the original
displayName.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

* chat: refresh hasCanDelegateProviders context key on programmatic register/unregister

Programmatic chat session contributions bypass _evaluateAvailability,
which was the only path that called _updateHasCanDelegateProvidersContextKey.
Update the context key directly in registerChatSessionContribution and its
dispose so UI gated on ChatContextKeys.hasCanDelegateProviders stays in sync.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: roblourens

src/vs/workbench/contrib/chat/browser/agentSessions/agentHost/agentHostChatContribution.ts

@@ -152,14 +152,22 @@ export class AgentHostContribution extends Disposable implements IWorkbenchContr
 		const agentId = sessionType;
 		const vendor = sessionType;
 
+		// In the Agents app, the agent-host displayName is unambiguous because
+		// only agent-host sessions exist there. In VS Code, the same picker
+		// also lists the extension-host harness with the same displayName
+		// (e.g. "Copilot CLI"), so suffix with "- Agent Host" to disambiguate.
+		const displayName = this._isSessionsWindow
+			? agent.displayName
+			: localize('agentHost.displayName', "{0} - Agent Host", agent.displayName);
+
 		// Chat session contribution.
 		// In the Agents app, hide the delegation picker for local agent host
 		// sessions (matches behavior of remote agent host sessions). In VS Code,
 		// keep the picker available so users can hand off to other targets.
 		store.add(this._chatSessionsService.registerChatSessionContribution({
 			type: sessionType,
 			name: agentId,
-			displayName: agent.displayName,
+			displayName,
 			description: agent.description,
 			canDelegate: true,
 			requiresCustomModels: true,

src/vs/workbench/contrib/chat/browser/chatSessions/chatSessions.contribution.ts

@@ -810,10 +810,19 @@ export class ChatSessionsService extends Disposable implements IChatSessionsServ
 		}
 
 		this._contributions.set(contribution.type, { contribution, extension: undefined });
+		// Programmatically-registered contributions are always considered
+		// available; mark them as such so the autorun in the constructor
+		// registers the in-place "New {0} Session" action for them. Without
+		// this, types like `agent-host-copilotcli` (registered by the local
+		// agent host) have no `openNewChatSessionInPlace.<type>` command.
+		this._contributionDisposables.set(contribution.type, new DisposableStore());
+		this._updateHasCanDelegateProvidersContextKey();
 		this._onDidChangeAvailability.fire();
 
 		return toDisposable(() => {
 			this._contributions.delete(contribution.type);
+			this._contributionDisposables.deleteAndDispose(contribution.type);
+			this._updateHasCanDelegateProvidersContextKey();
 			this._onDidChangeAvailability.fire();
 		});
 	}