fix(ocr): report the actual provider and PPTX failure location

HTTP OCR failures in PPTX parsing were incorrectly labeled as local OCR failures. Report the selected provider and slide/image location, and retain bounded structured server diagnostics with configured-key redaction and log IDs. Preserve existing fallback behavior.

Validation: 38 focused tests, typecheck and lint passed. Full test run timed out after 200 seconds. Synthetic service probes reproduced HTTP 500; the server-side failure remains unresolved.

Release note: PPTX parsing warnings now identify the actual OCR provider and failed image location, with server diagnostics for troubleshooting.

src/main/document-parsing-service.test.ts

@@ -1,10 +1,13 @@
-import { describe, expect, it, vi } from 'vitest'
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import { defaultHttpOcrSettings } from '../shared/document-parsing-contracts'
 import {
   defaultDocumentParsingSettings
 } from './document-parsing-settings-store'
 import { DocumentParsingService } from './document-parsing-service'
 import { createImagePptx } from '../../tests/support/pptx-fixture'
 
+afterEach(() => vi.unstubAllGlobals())
+
 function createPdfFixture(...pageTexts: string[]): Buffer {
   const texts = pageTexts.length > 0 ? pageTexts : ['']
   const fontObjectId = texts.length + 3
@@ -178,6 +181,22 @@ describe('DocumentParsingService', () => {
     expect(recognize).toHaveBeenCalledOnce()
   })
 
+  it('reports HTTP PPTX failures with the image location without consulting local OCR', async () => {
+    vi.stubGlobal('fetch', vi.fn(async () => Response.json({ errorCode: 500, errorMsg: 'Internal server error', logId: 'pptx-failure' }, { status: 500 })))
+    const { service, modelManager, recognize } = createService({ settings: {
+      ocrProvider: 'paddleocr-vl', httpOcr: { ...defaultHttpOcrSettings, baseUrl: 'http://ocr.test' }
+    } })
+    const bytes = createImagePptx('Useful native slide body')
+    const parsed = await service.parse('slides.pptx', bytes, 'chat-attachment')
+    expect(parsed.content).toContain('Useful native slide body')
+    expect(parsed.warnings).toEqual([
+      'HTTP OCR 未完成，已保留 PPTX 文本内容：幻灯片 1 · 图片 1：HTTP OCR /layout-parsing：HTTP 500；服务错误 500；Internal server error；logId: pptx-failure'
+    ])
+    await expect(service.parse('slides.pptx', bytes, 'knowledge-index')).rejects.toThrow('幻灯片 1 · 图片 1：HTTP OCR /layout-parsing：HTTP 500')
+    expect(modelManager.getStatus).not.toHaveBeenCalled()
+    expect(recognize).not.toHaveBeenCalled()
+  })
+
   it('keeps useful PDF text local without invoking OCR', async () => {
     const { recognize, service } = createService()