Simplify experience for no auto model

[pwang347]

No description provided.

[Copilot]

Pull request overview

This PR removes the “no Auto model”/“no models available” empty-state path from the chat model picker and instead shifts eligibility/upgrade handling toward session-type locking (notably for Copilot Free/EDU). It also simplifies the Sessions window model-picker integration by removing the showAutoModel option plumbing across providers.

Changes:

• Remove showAutoModel from model picker delegates/options and delete the associated empty-state behavior and tests.
• Introduce entitlement-based locking in the session-type picker for session types that can’t produce a request for Free/EDU users (no Auto fallback + no targeted/BYOK models).
• Simplify Sessions window send/model-picker gating logic and update Copilot session contribution metadata (supportsAutoModel).

Show a summary per file

File	Description
src/vs/workbench/contrib/chat/test/browser/widget/input/chatModelPicker.test.ts	Removes tests that asserted the “no models available” empty-state when Auto is unavailable.
src/vs/workbench/contrib/chat/browser/widget/input/sessionTargetPickerActionItem.ts	Adds model-aware entitlement locking for session types; updates upgrade hover copy.
src/vs/workbench/contrib/chat/browser/widget/input/modelPickerActionItem.ts	Removes showAutoModel from the model picker delegate API.
src/vs/workbench/contrib/chat/browser/widget/input/delegationSessionPickerActionItem.ts	Wires new DI dependency through to the base session-type picker.
src/vs/workbench/contrib/chat/browser/widget/input/chatModelPicker.ts	Removes the empty-state; always inserts a synthetic “Auto” entry when the model list is empty.
src/vs/workbench/contrib/chat/browser/widget/input/chatInputPart.ts	Removes “no usable model” send gating from context keys and related update calls.
src/vs/sessions/services/sessions/common/sessionsProvider.ts	Removes showAutoModel from session model picker options.
src/vs/sessions/contrib/providers/copilotChatSessions/browser/copilotChatSessionsProvider.ts	Simplifies model picker options returned by provider (drops showAutoModel).
src/vs/sessions/contrib/providers/agentHost/browser/baseAgentHostSessionsProvider.ts	Simplifies model picker options returned by provider (drops showAutoModel).
src/vs/sessions/contrib/chat/test/browser/modelPicker.test.ts	Deletes tests for sessionHasNoSelectableModel (function removed).
src/vs/sessions/contrib/chat/browser/newChatWidget.ts	Removes model-based can-send gating and related reactivity wiring.
src/vs/sessions/contrib/chat/browser/newChatInSessionWidget.ts	Removes model-based can-send gating and related reactivity wiring.
src/vs/sessions/contrib/chat/browser/newChatInput.ts	Removes the runtime canSendRequest guard from the send path (UI still disables button).
src/vs/sessions/contrib/chat/browser/modelPicker.ts	Hides/disables the picker when no models are offered; removes Auto/empty-state behavior.
extensions/copilot/package.json	Marks the Cloud agent session contribution as supportsAutoModel: false.

Copilot's findings

Comments suppressed due to low confidence (1)

src/vs/sessions/contrib/chat/browser/newChatInput.ts:604

• _send no longer checks options.canSendRequest, so the Enter/sendQuery paths can still dispatch a request even when the Send button is disabled (e.g. while the session is loading). This can lead to requests being sent in a state the UI is explicitly trying to block.

	private async _send(background = false): Promise<void> {
		const rawQuery = this._editor.getModel()?.getValue() ?? '';
		const query = rawQuery.trim();
		const queryOffset = rawQuery.length - rawQuery.trimStart().length;
		const hasSendableAttachment = this._contextAttachments.attachments.some(isExplicitFileOrImageVariableEntry);
		if ((!query && !hasSendableAttachment) || this._sending) {
			return;
		}

		// Check for slash commands first
		if (query && this._slashCommandHandler?.tryExecuteSlashCommand(query)) {
			this._editor.getModel()?.setValue('');
			return;
		}

• Files reviewed: 15/15 changed files
• Comments generated: 2

[github-actions]

Base: 8a492327 Current: 4a409ec2

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