feat(metadata): allow up to 3 previews per device type

[EvanBacon]

Summary

• Lift the hard-coded single-preview-per-PreviewType limit in metadata:push/metadata:pull. Apple supports up to 3 video previews per device type; we now sync all of them.
• ApplePreviews accepts either a single ApplePreviewConfig (legacy form, still works) or an array of configs. Existing store.config.json files using the single-object form continue to parse and push without changes.
• metadata:pull mirrors how screenshots are emitted: 0 -> omitted, 1 -> single object (back-compat), 2+ -> array. Order is preserved.
• metadata:push now mirrors the screenshots sync pipeline for previews: match existing previews by fileName + fileSize + completion state, upload only changed entries, delete removed ones, and reorder via AppPreviewSet.reorderPreviewsAsync to match config order. Existing previews with only a previewFrameTimeCode change are patched in place.
• JSON schema (schema/metadata-0.json) updated to allow either form for each preview type.

Test plan

• yarn jest src/metadata/apple/tasks/__tests__/previews.test.ts — 16 passing, including new cases:
  • single string preview (legacy)
  • single object preview with previewFrameTimeCode (legacy)
  • multi-preview array with mixed string + object entries
  • reorder when ASC ordering differs from config
  • empty array short-circuits without uploading
  • downloadAsync emits an array when a set has multiple previews
• yarn jest src/metadata/apple/config — reader/writer tests still pass (63)
• yarn lint on changed files — no errors (only the same pre-existing no-unnecessary-type-assertion warning that already exists in screenshots.ts)
• yarn fmt applied
• Manual metadata:pull against an app that has multiple previews per device type
• Manual metadata:push with both single-object and array forms in store.config.json

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File Patterns	Mentions
**/*	@douglowder
packages/eas-cli/schema/**	@byCedric
packages/eas-cli/src/metadata/**	@byCedric

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Codecov Report

❌ Patch coverage is 72.22222% with 25 lines in your changes missing coverage. Please review.
✅ Project coverage is 54.30%. Comparing base (8c170af) to head (608bb66).

Files with missing lines	Patch %	Lines
...ckages/eas-cli/src/metadata/apple/config/writer.ts	0.00%	17 Missing ⚠️
...kages/eas-cli/src/metadata/apple/tasks/previews.ts	89.05%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3593      +/-   ##
==========================================
+ Coverage   54.26%   54.30%   +0.05%     
==========================================
  Files         821      821              
  Lines       35327    35383      +56     
  Branches     7363     7381      +18     
==========================================
+ Hits        19166    19212      +46     
- Misses      16074    16084      +10     
  Partials       87       87              

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