[PLT-0] update test assets

[mrobers1982]

Description

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Fixes # (issue)

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Note

Low Risk
Test-only changes that swap referenced remote fixtures; risk is limited to potential test flakiness if the new hosted assets/URLs are unavailable or differ in format.

Overview
Switches test fixtures and integration tests to use a new set of hosted media assets (video/audio/HTML/text/PDF/conversational and a segmentation mask), including updating image_url to use IMG_URL instead of a dedicated maskable image.

Removes the unused llm_human_preference_data_row_factory fixture and updates PDF URL references used in data-row update/upsert attachment assertions.

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Cursor Bugbot has reviewed your changes and found 1 potential issue.

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Segmentation mask replaced with regular photo image

Medium Severity

The segmentation mask instanceURI was changed from raster_seg.png (a purpose-built binary segmentation mask) to dog.png (likely a regular photograph). Segmentation masks work by using colorRGB (here (255, 255, 255)) to identify which pixels belong to the segmented region. A regular dog photo is unlikely to have meaningful pure-white pixels, resulting in an empty or nonsensical segmentation — potentially causing test failures or silently making the tests meaningless.

 

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[mrobers1982]

Yeah, not sure it matters for this test - let's see what happens.