fix: image serialization

[kswenson]

[CODAP-1074] Image tile serialization of dropped images is broken

[codecov]

Codecov Report

❌ Patch coverage is 82.66667% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 86.76%. Comparing base (6bd01be) to head (7539011).
⚠️ Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
v3/src/hooks/use-import-helpers.ts	11.11%	8 Missing ⚠️
v3/src/utilities/image-utils.ts	90.19%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2295      +/-   ##
==========================================
+ Coverage   86.75%   86.76%   +0.01%     
==========================================
  Files         724      724              
  Lines       38741    38810      +69     
  Branches     9586     9595       +9     
==========================================
+ Hits        33608    33674      +66     
- Misses       4829     5127     +298     
+ Partials      304        9     -295     

Flag	Coverage Δ
cypress	72.02% <1.35%> (-0.13%)	⬇️
jest	55.67% <82.66%> (+0.05%)	⬆️

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[cypress]

codap-v3    Run #9573

Run Properties:   Passed #9573  •  7539011dde: chore: add Copilot-written test suite

Project	codap-v3
Branch Review	CODAP-1074-image-serialization
Run status	Passed #9573
Run duration	08m 09s
Commit	7539011dde: chore: add Copilot-written test suite
Committer	Kirk Swenson
View all properties for this run ↗︎

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Test results
Failures	0
Flaky	3
Pending	48
Skipped	0
Passing	301
View all changes introduced in this branch ↗︎

[Copilot]

Pull request overview

This PR fixes image serialization by converting images to data URLs instead of using ephemeral object URLs, enabling proper persistence and export of image tiles.

Changes:

• Adds utility functions to convert files to data URLs and downscale large images to prevent bloat
• Updates image import to use data URLs with automatic downscaling to 512px max dimension
• Ensures image tiles export correctly as DG.ImageComponentView type in v2 format

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
v3/src/utilities/importable-files.ts	Adds stripExtensionFromFilename utility to extract clean filename for image titles
v3/src/utilities/importable-files.test.ts	Tests for the new filename stripping utility
v3/src/utilities/image-utils.ts	Adds fileToDataUrl and downscaleImageFile functions for image conversion and size optimization
v3/src/utilities/image-utils.test.ts	Tests for data URL conversion and downscaling functions
v3/src/hooks/use-import-helpers.ts	Updates image import to use data URLs instead of object URLs, adds filename as title
v3/src/components/web-view/web-view-registration.ts	Fixes image export to use correct DG.ImageComponentView component type
v3/src/components/web-view/web-view-registration.test.ts	Updates and adds tests for image tile export verification

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[bfinzer]

👍🏻LGTM
I'm going to write a new story describing the problem when running on MacOS26.