fix: resolve retain cycle in GutenbergCoverUploadProcessor

[amanjeetsingh150]

Summary

Report:

xctestleaks-artifacts.zip

Fixes #25441

The lazy var coverBlockProcessor in GutenbergCoverUploadProcessor created a GutenbergBlockProcessor with a replacer closure that strongly captured self, while self strongly held coverBlockProcessor, forming a retain cycle that prevented deallocation after every cover block upload.

Cycle:

GutenbergCoverUploadProcessor
  → lazy var coverBlockProcessor (strong)
    → GutenbergBlockProcessor.replacer closure (strong)
      → self (GutenbergCoverUploadProcessor) ← cycle back

Fix: add [weak self] to the replacer closure.

Verification

Detected and verified using XCTestLeaks a tool I am working to get leaks from unit tests.

Test	Before	After
testCoverBlockProcessor	leaks=1	leaks=0 ✅
testCoverBlockProcessorWithOtherAttributes	leaks=2	leaks=0 ✅
testDeepNestedCoverBlockProcessor	leaks=3	leaks=0 ✅
testImageCoverInVideoCoverBlockProcessor	leaks=4	leaks=0 ✅
testMultipleCoverBlocksProcessor	leaks=5	leaks=0 ✅
testNestedCoverBlockProcessor	leaks=5	leaks=0 ✅
testUpdateOuterCoverBlockProcessor	leaks=7	leaks=0 ✅
testVideoCoverBlockProcessor	leaks=7	leaks=0 ✅
testVideoCoverInImageCoverBlockProcessor	leaks=7	leaks=0 ✅

Test plan

• All GutenbergCoverUploadProcessorTests pass with leaks=0
• No functional behaviour changed — [weak self] with guard let self maintains the same logic

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[kean]

Good find, @amanjeetsingh150. Thank you!

[amanjeetsingh150]

Hey @kean, I see the auto merge didn't trigger is it because of the checks are stuck? Is there anything I can do from my side to unblock this.

[kean]

Hold on. There is some protections in place to allow only certain builds to run. I'm going to verify it and merge locally. Thank you.

[kean]

Hey, I merged the changes via #25455 (the commit attribution is in tact). Thank you.

[amanjeetsingh150]

Thanks @kean appreciated! 🙌