fix(attachment): reclaim applied previews on unmount

[IzumiSy]

Motivation

useAttachment retains image previews after a successful applyChanges() call, but clears the corresponding buffered upload operations. Its unmount cleanup previously read only that operation buffer, so successfully applied images no longer had their Blob URLs reclaimed when the hook unmounted.

This extracts the Attachment cleanup from #525 into an independent, small bug-fix PR based on main. It does not depend on the test-cleanup PR or include the lint upgrade and other state-ownership changes.

Design Decision

Track preview lifetime separately from pending operations

Keep a registry of Blob URLs created by this hook. Successful applies leave the previews usable, deletion releases and removes a URL, and unmount releases the remaining registered URLs. Caller-supplied initial URLs are not registered for unmount cleanup.

The existing operation buffering, rollback, and concurrent-flush behavior remain unchanged. No public API changes are needed.

Summary

• Reclaim image preview URLs on unmount even after their upload operations have been successfully applied.
• Cover pending/applied previews, caller-supplied URLs, and avoiding a second release of deleted previews.
• Add a patch changeset for the resource leak fix.

[github-actions]

Code Metrics Report

	main (589a66f)	#601 (2a32049)	+/-
Coverage	88.7%	88.7%	+0.0%
Test Execution Time	2m21s	2m14s	-7s

Details

  |                     | main (589a66f) | #601 (2a32049) |  +/-  |
  |---------------------|----------------|----------------|-------|
+ | Coverage            |          88.7% |          88.7% | +0.0% |
  |   Files             |            208 |            208 |     0 |
  |   Lines             |           6282 |           6284 |    +2 |
+ |   Covered           |           5574 |           5576 |    +2 |
+ | Test Execution Time |          2m21s |          2m14s |   -7s |

Code coverage of files in pull request scope (100.0% → 100.0%, patch 100.0%)

Files	Coverage	+/-	Patch Coverage	Status
packages/core/src/components/attachment/use-attachment.ts	100.0%	0.0%	100.0%	modified

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Reported by octocov

[IzumiSy]

/review

[github-actions]

✅ Code Review completed successfully!

Code review complete for PR #601 - no actionable High/Medium issues found in changed packages/core attachment hook behavior, and this workflow does not expose a general PR comment tool for approval-only reviews.

Generated by Code Review for #601

[Copilot]

🟢 Approval recommended

The ownership-based cleanup is correct, narrowly scoped, and covered by relevant lifecycle tests.

0 open findings

What changed in this PR

Fixes Blob URL leaks by tracking attachment previews independently from buffered operations.

Changes:

• Reclaims pending and applied previews on unmount.
• Prevents double revocation after deletion.
• Adds regression tests and a patch changeset.

File	Description
use-attachment.ts	Tracks and releases hook-owned preview URLs.
use-attachment.test.ts	Tests cleanup across apply, delete, and unmount.
.changeset/​tidy-otters-rest.md	Documents the patch release.

🧠 Review effort: Balanced

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