feat(logging-p0): add screenshot capture and browser console diagnostics for ERP errors

Enhance ERP automation error diagnostics by capturing PNG screenshots
on every error and forwarding browser console warnings/errors to the
structured logger. Includes automatic cleanup of old screenshots
aligned with the configured log retention period.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/main/services/erp/erp-error-context.ts

@@ -6,12 +6,61 @@
  */
 
 import type { Page } from 'playwright'
+import fs from 'fs'
+import path from 'path'
+import { getLogDir } from '../logger/shared'
 
 export interface ErpErrorContext {
   pageUrl?: string
   frameHierarchy?: Array<{ name: string; url: string }>
   targetSelector?: string
   step?: string
+  screenshotPath?: string
+}
+
+/**
+ * Sanitize a step name for use as a filename component.
+ * Replaces non-alphanumeric characters with underscores and truncates.
+ */
+function sanitizeForFilename(step: string | undefined): string {
+  if (!step) return 'unknown'
+  return step.replace(/[^a-zA-Z0-9_-]/g, '_').slice(0, 40)
+}
+
+/**
+ * Capture a screenshot of the page for error diagnostics.
+ * Stored as PNG under <logDir>/screenshots/.
+ * Defensive: never throws.
+ */
+async function captureScreenshot(page: Page, step?: string): Promise<string | undefined> {
+  try {
+    if (page.isClosed()) return undefined
+
+    const screenshotDir = path.join(getLogDir(), 'screenshots')
+    fs.mkdirSync(screenshotDir, { recursive: true })
+
+    const now = new Date()
+    const timestamp = [
+      now.getFullYear(),
+      String(now.getMonth() + 1).padStart(2, '0'),
+      String(now.getDate()).padStart(2, '0'),
+      '_',
+      String(now.getHours()).padStart(2, '0'),
+      String(now.getMinutes()).padStart(2, '0'),
+      String(now.getSeconds()).padStart(2, '0')
+    ].join('')
+
+    const filename = `err_${timestamp}_${sanitizeForFilename(step)}.png`
+    const filePath = path.join(screenshotDir, filename)
+
+    const buffer = await page.screenshot({ type: 'png', timeout: 5000 })
+    fs.writeFileSync(filePath, buffer)
+
+    return filePath
+  } catch {
+    // screenshot failure must not propagate
+    return undefined
+  }
 }
 
 /**
@@ -49,5 +98,7 @@ export async function capturePageContext(
     ctx.step = step
   }
 
+  ctx.screenshotPath = await captureScreenshot(page, step)
+
   return ctx
 }