record download-file: Image column download fails with 'No FileAttachment records found'

[TomProkop]

Description

txc env data record upload-file reports success when uploading to an image column, but download-file then fails with a FileAttachment lookup error. The round-trip (upload → download) is broken for image columns, while file columns work correctly.

Steps to Reproduce

# 1. Upload a PNG to an image column — reports success:
txc env data record upload-file \
  --entity txcv3_valv3rt1434 \
  --record-id 11ad3537-704c-f111-bec7-6045bde02116 \
  --column txcv3_imagefield \
  --file ./test-image.png \
  --allow-production
# Output: Uploaded 'test-image.png' to txcv3_valv3rt1434/.../txcv3_imagefield

# 2. Download the same image — fails:
txc env data record download-file \
  --entity txcv3_valv3rt1434 \
  --record-id 11ad3537-704c-f111-bec7-6045bde02116 \
  --column txcv3_imagefield \
  --output ./downloaded-image.png \
  --allow-production

Expected Behavior

Download should retrieve the uploaded image and save it to the output path.

Actual Behavior

No FileAttachment records found for imagedescriptorId: 13f5eddc-714c-f111-bec6-7c1e52766187
for image attribute: txcv3_imagefield of txcv3_valv3rt1434 record with id 11ad3537-...

Analysis

Querying the record shows txcv3_imagefield: "System.Byte[]" — the image data was stored in the legacy binary format. The download command looks for a FileAttachment record (which is the modern storage mechanism for CanStoreFullImage=true columns), but finds none.

Possible causes:

1. Upload stored the image in the old binary format instead of as a FileAttachment
2. Download uses FileAttachment lookup but should also handle the legacy binary format
3. Image columns may require a different API path (/entityimage vs /) than file columns

Comparison: File column works correctly

# File upload + download round-trip works perfectly:
txc env data record upload-file --column txcv3_filefield ...   # ✅ Succeeds
txc env data record download-file --column txcv3_filefield ... # ✅ Succeeds, content matches

Impact

🟡 Medium — File columns work correctly. Only image columns are affected.

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Found during PR #67 (pp-entity-attribute) CRUD validation on https://udpp26-txc-demo.crm4.dynamics.com.

[zekelinAlex]

Tested this on master and the image download-file round-trip works fine, so there's no actual bug here.

the only real difference from the repro is that --record-id was a positional argument, not a flag. added the flag (with a --record alias) in #165