fix: cancel offscreen media downloads

[agent-p1p]

Summary

• retain each tile's automatic media download task
• cancel queued or in-flight work when the tile scrolls out, disappears, or changes attachment
• add a regression check for the SwiftUI cancellation wiring

Test plan

• source contract regression check passes
• git diff --check
• macOS build/tests deferred to GitHub CI (Xcode unavailable on Linux)

Fixes #468

---

[coderabbitai]

Warning

Review limit reached

@mubarakcoded, you've reached your PR review limit, so we couldn't start this review.

Next review available in: 50 minutes

Enable usage-based reviews in Billing to review now. Otherwise, wait until the next included review is available.
You're only billed for reviews past your plan's rate limits ($0.25/file).

How can I continue?

After more reviews become available, a review can be triggered using the @coderabbitai review command as a PR comment. Alternatively, push new commits to this PR.

To avoid repeated limits, reduce automatic review volume by pausing incremental auto-reviews earlier, using label-based review opt-in, excluding WIP or generated PR titles, or requesting reviews manually when the PR is ready. If your team needs uninterrupted high-volume reviews, an organization admin can enable usage-based reviews.

How do review limits work?

CodeRabbit enforces per-developer PR review limits for each organization. Most developers receive the normal plan review availability.

For paid Pro and Pro+ PR reviews, CodeRabbit uses adaptive limits for sustained high-volume activity. When a developer's recent PR review activity reaches the 95th percentile or higher among CodeRabbit users, additional reviews become available more gradually as earlier reviews age out of the rolling window.

Please refer docs for additional details.

Review details

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: b1b6c775-6e75-4183-ac37-8057457fbd8c

📥 Commits

Reviewing files that changed from the base of the PR and between 490ca5b and 04948d8.

📒 Files selected for processing (2)

• whitenoise-mac/Views/MessageMediaViews.swift
• whitenoise-macTests/whitenoise_macTests.swift

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch pip/whitenoise-mac-468

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[stage-review]

Ready to review this PR? Stage has broken it down into 2 individual chapters for you:

	Title
1	Manage media download task lifecycle
2	Verify download cancellation via source contract test

_{Chapters generated by Stage for commit 04948d8 on Jul 13, 2026 12:41pm UTC.}