Add diagnostics action for chat customizations

[pwang347]

[Copilot]

Pull request overview

Adds a new chat slash command (/config-info) intended to display diagnostic/status information about chat prompt-related configuration and discovered files (agents, instructions, prompt files, skills, and special instruction files).

Changes:

• Registers a new workbench contribution for the /config-info slash command.
• Implements the /config-info command logic to enumerate configured source folders and discovered prompt-related files.
• Formats the collected status into a markdown tree rendered in chat.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 7 comments.

File	Description
src/vs/workbench/contrib/chat/browser/chat.contribution.ts	Wires the new ChatConfigInfoSlashCommandContribution into the workbench contributions so the command is available.
src/vs/workbench/contrib/chat/browser/actions/chatConfigInfoSlashCommand.ts	Implements command registration, discovery of prompt/agent/instruction/skill files, and markdown output formatting.

Comments suppressed due to low confidence (4)

src/vs/workbench/contrib/chat/browser/actions/chatConfigInfoSlashCommand.ts:221

• displayPath: 'User Data' is shown to users in the markdown output but isn't localized. Please use nls.localize(...) (or reuse the existing localized label used elsewhere, e.g. promptsServiceImpl.ts:595) for this label.

	paths.push({ uri: userDataPromptsHome, exists: userDataExists, storage: PromptsStorage.user, scanOrder: scanOrder++, displayPath: 'User Data', isDefault: true });

src/vs/workbench/contrib/chat/browser/actions/chatConfigInfoSlashCommand.ts:96

• The fallback error report uses a hard-coded user-facing label ("Error:") and string interpolation. Please localize the message via nls.localize and use a placeholder for the error text so it can be translated correctly.

					content: new MarkdownString(`**Error:** ${e instanceof Error ? e.message : String(e)}`),
					kind: 'markdownContent'

src/vs/workbench/contrib/chat/browser/actions/chatConfigInfoSlashCommand.ts:436

• displayPath: 'User Data' is user-facing and should be localized (or reused from existing localized labels) for consistency with the rest of the output.

	paths.push({ uri: userDataPromptsHome, exists: userDataExists, storage: PromptsStorage.user, scanOrder: scanOrder++, displayPath: 'User Data', isDefault: true });

src/vs/workbench/contrib/chat/browser/actions/chatConfigInfoSlashCommand.ts:808

• The fallback extension group key uses the hard-coded string 'unknown', which is rendered to users in the markdown output. Please localize this (and/or avoid showing a sentinel value) so the output is consistent with other localized labels.

				const extId = file.extensionId || 'unknown';
				if (!filesByExtension.has(extId)) {