Media: Exclude IMG from crossorigin injection in media templates

[itzmekhokan]

Media library picker previews break for media served from a CDN (or any host without CORS headers) because wp_print_media_templates() injects crossorigin="anonymous" on IMG tags in the media manager Backbone templates.

What the problem was:

• When the client-side media processing feature was re-introduced in trunk, wp_print_media_templates() began adding crossorigin="anonymous" to AUDIO, IMG, and VIDEO tags in the media templates.
• This reintroduced, for the media library picker, the exact issue already fixed for wp_add_crossorigin_attributes() in [62048] (#64886).
• Under Document-Isolation-Policy: isolate-and-credentialless the browser loads cross-origin images in credentialless mode without CORS headers. Forcing crossorigin="anonymous" on IMG triggers a CORS request that fails for images served without Access-Control-Allow-Origin headers, so offloaded media previews break.

What the fix does:

• Removes IMG from the tags that receive crossorigin="anonymous" in wp_print_media_templates(), so it matches wp_add_crossorigin_attributes().
• AUDIO and VIDEO tags continue to receive the attribute, unchanged.
• Adds a code comment explaining why IMG is excluded, to prevent recurrence.

Approach and why:

• Mirrors the established, intentional behaviour from [62048]; it is the minimal one-list change that resolves the regression without touching audio/video handling or the output-buffer path.

Trac ticket: https://core.trac.wordpress.org/ticket/65673

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus 4.8
Used for: Ticket analysis, writing the unit tests, and PR Description. All changes were reviewed by me.

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