fix(test): resolve CI failures from the overhaul

- fixture-integrity: probe media via media-engine probeMedia (resolves the
  bundled static ffmpeg) instead of bare system ffprobe, which is ENOENT in CI;
  gate on ffmpegAvailable() like the other media tests
- a11y: regenerate a11y-baseline.json to include the mobile device keys (the
  baseline only had desktop keys, so the mobile a11y scan saw them as new)
- device-visual: tag @visual and exclude it from the PR mobile-smoke gate
  (darwin-only screenshots cannot pass on linux; nightly + update-visual-baselines
  still run it to seed linux goldens)

tests/e2e/a11y-baseline.json

@@ -140,6 +140,131 @@
       "impact": "moderate",
       "description": "Ensure all skip links have a focusable target",
       "count": 1
+    },
+    "mobile-home-en:color-contrast": {
+      "impact": "serious",
+      "description": "Ensure the contrast between foreground and background colors meets WCAG 2 AA minimum contrast ratio thresholds",
+      "count": 7
+    },
+    "mobile-home-en:heading-order": {
+      "impact": "moderate",
+      "description": "Ensure the order of headings is semantically correct",
+      "count": 1
+    },
+    "mobile-image-resize-en:color-contrast": {
+      "impact": "serious",
+      "description": "Ensure the contrast between foreground and background colors meets WCAG 2 AA minimum contrast ratio thresholds",
+      "count": 2
+    },
+    "mobile-image-resize-en:link-name": {
+      "impact": "serious",
+      "description": "Ensure links have discernible text",
+      "count": 1
+    },
+    "mobile-video-convert-en:color-contrast": {
+      "impact": "serious",
+      "description": "Ensure the contrast between foreground and background colors meets WCAG 2 AA minimum contrast ratio thresholds",
+      "count": 2
+    },
+    "mobile-video-convert-en:link-name": {
+      "impact": "serious",
+      "description": "Ensure links have discernible text",
+      "count": 1
+    },
+    "mobile-audio-convert-en:color-contrast": {
+      "impact": "serious",
+      "description": "Ensure the contrast between foreground and background colors meets WCAG 2 AA minimum contrast ratio thresholds",
+      "count": 2
+    },
+    "mobile-audio-convert-en:link-name": {
+      "impact": "serious",
+      "description": "Ensure links have discernible text",
+      "count": 1
+    },
+    "mobile-document-pdf-to-image-en:color-contrast": {
+      "impact": "serious",
+      "description": "Ensure the contrast between foreground and background colors meets WCAG 2 AA minimum contrast ratio thresholds",
+      "count": 2
+    },
+    "mobile-document-pdf-to-image-en:link-name": {
+      "impact": "serious",
+      "description": "Ensure links have discernible text",
+      "count": 1
+    },
+    "mobile-data-csv-excel-en:color-contrast": {
+      "impact": "serious",
+      "description": "Ensure the contrast between foreground and background colors meets WCAG 2 AA minimum contrast ratio thresholds",
+      "count": 2
+    },
+    "mobile-data-csv-excel-en:link-name": {
+      "impact": "serious",
+      "description": "Ensure links have discernible text",
+      "count": 1
+    },
+    "mobile-editor-en:page-has-heading-one": {
+      "impact": "moderate",
+      "description": "Ensure that the page, or at least one of its frames contains a level-one heading",
+      "count": 1
+    },
+    "mobile-editor-en:region": {
+      "impact": "moderate",
+      "description": "Ensure all page content is contained by landmarks",
+      "count": 1
+    },
+    "mobile-editor-en:skip-link": {
+      "impact": "moderate",
+      "description": "Ensure all skip links have a focusable target",
+      "count": 1
+    },
+    "mobile-login-en:color-contrast": {
+      "impact": "serious",
+      "description": "Ensure the contrast between foreground and background colors meets WCAG 2 AA minimum contrast ratio thresholds",
+      "count": 1
+    },
+    "mobile-login-en:region": {
+      "impact": "moderate",
+      "description": "Ensure all page content is contained by landmarks",
+      "count": 1
+    },
+    "mobile-login-en:skip-link": {
+      "impact": "moderate",
+      "description": "Ensure all skip links have a focusable target",
+      "count": 1
+    },
+    "mobile-home-ar:color-contrast": {
+      "impact": "serious",
+      "description": "Ensure the contrast between foreground and background colors meets WCAG 2 AA minimum contrast ratio thresholds",
+      "count": 8
+    },
+    "mobile-home-ar:heading-order": {
+      "impact": "moderate",
+      "description": "Ensure the order of headings is semantically correct",
+      "count": 1
+    },
+    "mobile-image-resize-ar:color-contrast": {
+      "impact": "serious",
+      "description": "Ensure the contrast between foreground and background colors meets WCAG 2 AA minimum contrast ratio thresholds",
+      "count": 1
+    },
+    "mobile-image-resize-ar:link-name": {
+      "impact": "serious",
+      "description": "Ensure links have discernible text",
+      "count": 1
+    },
+    "mobile-login-ar:color-contrast": {
+      "impact": "serious",
+      "description": "Ensure the contrast between foreground and background colors meets WCAG 2 AA minimum contrast ratio thresholds",
+      "count": 1
+    },
+    "mobile-login-ar:region": {
+      "impact": "moderate",
+      "description": "Ensure all page content is contained by landmarks",
+      "count": 1
+    },
+    "mobile-login-ar:skip-link": {
+      "impact": "moderate",
+      "description": "Ensure all skip links have a focusable target",
+      "count": 1
     }
   }
 }