feat(ai): show lint details on demand in the chat

The lint tool call rendered as a bare summary line with nothing behind it.
Mark it as having details so the individual problems can be opened, and pass
the formatted output as the tool result — without it the details panel reads
"No result yet". Details stay collapsed on success, since the header already
carries the counts.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/lib/components/copilot/chat/global/core.test.ts

@@ -245,6 +245,19 @@ vi.mock('./rawAppBundlerBridge', () => ({
 	}))
 }))
 
+// Monaco cannot load in the node test environment, and core.ts imports the lint
+// service lazily precisely to keep it out of this import graph.
+vi.mock('$lib/components/lint/headlessLint', () => ({
+	canLintHeadless: (lang: string) => lang === 'bun',
+	lintCode: vi.fn(async () => ({
+		errorCount: 1,
+		warningCount: 0,
+		errors: [{ startLineNumber: 2, message: "Type 'string' is not assignable to type 'number'." }],
+		warnings: [],
+		contentMismatch: false
+	}))
+}))
+
 vi.mock('$lib/infer', async () => ({
 	...(await vi.importActual<any>('$lib/infer')),
 	// Avoid the wasm parser in unit tests: the script deploy path infers the arg
@@ -433,6 +446,26 @@ describe('global AI tools', () => {
 		)
 	})
 
+	it('surfaces lint output as the tool result so the details panel can show it', async () => {
+		vi.mocked(ScriptService.getScriptByPath).mockResolvedValueOnce({
+			path: 'u/admin/probe',
+			content: 'const a: number = "x"',
+			language: 'bun',
+			summary: ''
+		} as any)
+
+		const result = await callGlobalTool('get_lint_errors', {
+			kind: 'script',
+			path: 'u/admin/probe'
+		})
+
+		expect(result).toContain("Type 'string' is not assignable to type 'number'.")
+		expect(toolCallbacks.setToolStatus).toHaveBeenCalledWith(
+			'test-get_lint_errors',
+			expect.objectContaining({ result })
+		)
+	})
+
 	it('defaults list_runs to 30 results when no limit is given', async () => {
 		await callGlobalTool('list_runs', {})
 		expect(JobService.listJobs).toHaveBeenCalledWith(

frontend/src/lib/components/copilot/chat/global/core.ts

@@ -2751,6 +2751,9 @@ export const globalTools: Tool<{}>[] = [
 			'get_lint_errors',
 			'Type-check a script, flow module, or raw app backend runnable and report its errors and warnings. Supports TypeScript, JavaScript, Python, Go, Deno and Bash.'
 		),
+		// The header carries the counts; the individual problems are worth a look but not
+		// worth the vertical space by default.
+		showDetails: true,
 		fn: async (ctx) => {
 			const parsed = getLintErrorsSchema.parse(ctx.args)
 			return getLintErrors(parsed, ctx)
@@ -3812,12 +3815,20 @@ async function checkAppFrontend(path: string, ctx: WriteDraftCtx): Promise<strin
 	const value = await loadAppValueForRead(path, workspace)
 	try {
 		await bundleRawAppDraft({ workspace, files: value.files })
-		toolCallbacks.setToolStatus(toolId, { content: `Frontend of app "${path}" compiles` })
-		return '✅ The app frontend compiles with no errors.'
+		const response = '✅ The app frontend compiles with no errors.'
+		toolCallbacks.setToolStatus(toolId, {
+			content: `Frontend of app "${path}" compiles`,
+			result: response
+		})
+		return response
 	} catch (e) {
 		const message = e instanceof Error ? e.message : String(e)
-		toolCallbacks.setToolStatus(toolId, { content: `Frontend of app "${path}" failed to compile` })
-		return `❌ The app frontend failed to compile:\n\n${message}`
+		const response = `❌ The app frontend failed to compile:\n\n${message}`
+		toolCallbacks.setToolStatus(toolId, {
+			content: `Frontend of app "${path}" failed to compile`,
+			result: response
+		})
+		return response
 	}
 }
 
@@ -3835,10 +3846,12 @@ async function getLintErrors(args: LintTargetArgs, ctx: WriteDraftCtx): Promise<
 	const { canLintHeadless, lintCode } = await import('$lib/components/lint/headlessLint')
 
 	if (!canLintHeadless(target.language)) {
+		const response = `Linting ${target.language} is not supported. Do not retry; verify the code by test-running it instead.`
 		toolCallbacks.setToolStatus(toolId, {
-			content: `Lint unavailable for ${target.language}`
+			content: `Lint unavailable for ${target.language}`,
+			result: response
 		})
-		return `Linting ${target.language} is not supported. Do not retry; verify the code by test-running it instead.`
+		return response
 	}
 
 	toolCallbacks.setToolStatus(toolId, { content: `Linting ${target.label}...` })
@@ -3855,8 +3868,6 @@ async function getLintErrors(args: LintTargetArgs, ctx: WriteDraftCtx): Promise<
 			: result.warningCount > 0
 				? `${result.warningCount} warning(s)`
 				: 'no issues'
-	toolCallbacks.setToolStatus(toolId, { content: `Linted ${target.label}: ${summary}` })
-
 	let response = formatScriptLintResult(result)
 	if (result.unavailableServers?.length) {
 		response += `\n\nNote: the ${result.unavailableServers.join(' and ')} language server${result.unavailableServers.length > 1 ? 's did' : ' did'} not respond, so some problems may not be listed. Treat a clean result as inconclusive.`
@@ -3864,6 +3875,11 @@ async function getLintErrors(args: LintTargetArgs, ctx: WriteDraftCtx): Promise<
 	if (result.contentMismatch) {
 		response += `\n\nNote: an editor is currently open on this code and its buffer differs from the draft. The results above are for what that editor shows.`
 	}
+	// The result has to reach the tool display, or its details panel reads "No result yet".
+	toolCallbacks.setToolStatus(toolId, {
+		content: `Linted ${target.label}: ${summary}`,
+		result: response
+	})
 	return response
 }