Detect extension-sourced items in provider path for correct grouping

[joshspicer]

Fixes extension-sourced items being misclassified in the Chat Customizations provider path (microsoft/vscode-internalbacklog#7330).

Commits

• Detect extension-sourced items in provider path for correct grouping — Items from VS Code extensions (under ~/.vscode*/extensions/) were classified as "User". Now uses extractExtensionIdFromPath() to detect extension directories by finding extensions in the path segments and extracting the extension ID (stripping the version suffix). Default chat extension items → Built-in; other extensions → Extensions. Includes unit tests (8 test cases). Fixes microsoft/vscode-internalbacklog#7330

• Make built-in and extension items read-only in provider path — Provider-path items with groupKey: 'builtin' had no storage set, so the delete action's when-clause didn't hide the delete button. Now uses storage ?? groupKey for the context key overlay, so built-in and extension items correctly suppress delete/modify actions. Fixes microsoft/vscode-internalbacklog#7330

[Copilot]

Pull request overview

This PR fixes mis-grouping of extension-contributed Chat Customizations when using an external provider (e.g. Copilot CLI) by inferring “Extensions” vs “Built-in” from file: URIs that point into the local extensions install directory.

Changes:

• Extend _inferStorageAndGroup to detect .../extensions/<extId>-<version>/... and classify items as PromptsStorage.extension.
• Special-case the default chat extension to group its items under Built-in instead of Extensions.

Show a summary per file

File	Description
src/vs/workbench/contrib/chat/browser/aiCustomization/aiCustomizationListWidget.ts	Adds extension-install-directory detection to provider-path storage inference to group extension-sourced items correctly.

Copilot's findings

Comments suppressed due to low confidence (1)

src/vs/workbench/contrib/chat/browser/aiCustomization/aiCustomizationListWidget.ts:1803

• In the built-in extension case, _inferStorageAndGroup returns only { groupKey: BUILTIN_STORAGE } and leaves storage undefined. In the provider path that means AI_CUSTOMIZATION_ITEM_STORAGE_KEY is not set for these items, so context-menu when-clauses (e.g. deletable checks) will treat them like normal provider items and may incorrectly allow actions like Delete/Reveal/Edit. Keep storage as PromptsStorage.extension while overriding grouping via groupKey (and/or set an explicit read-only storage key) so built-in items remain correctly treated as extension-sourced/read-only.

			const versionMatch = folderName.match(/^(.+)-\d+\./);
			const extensionId = versionMatch ? versionMatch[1] : folderName;
			if (this.isChatExtensionItem(new ExtensionIdentifier(extensionId))) {
				return { groupKey: BUILTIN_STORAGE };
			}
			return { storage: PromptsStorage.extension };

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