refactor: clarify fileCreate() condition by making the specific case explicit

[miaulalala]

Summary

The original condition in FilesHooks::fileCreate() used a double-negative (De Morgan) form:

// Before — hard to parse: "unless identifier is empty AND it's a public token"
if ($this->currentUser->getUserIdentifier() !== '' || !$this->currentUser->isPublicShareToken()) {
    // regular upload
} else {
    // public upload
}

Rewritten as a direct positive check, with the specific case (public upload) as the if-branch:

// After — reads naturally
if ($this->currentUser->getUserIdentifier() === '' && $this->currentUser->isPublicShareToken()) {
    // public upload
} else {
    // regular upload
}

Also adds the missing fourth test case: a non-empty identifier combined with isPublicShareToken=true (a logged-in user uploading to a public share link) → treated as a regular upload.

No behaviour change.

Test plan

• All testFileCreate cases (4 data rows × 2 root tests = 6 assertions) — green

🤖 Generated with Claude Code

[cypress]

Activity    Run #3707

Run Properties:   Passed #3707  •  4744d6ecde: refactor: clarify fileCreate() condition by making the specific case explicit

Project	Activity
Branch Review	refactor/file-create-condition
Run status	Passed #3707
Run duration	02m 17s
Commit	4744d6ecde: refactor: clarify fileCreate() condition by making the specific case explicit
Committer	Anna
View all properties for this run ↗︎

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Test results
Failures	0
Flaky	0
Pending	1
Skipped	0
Passing	9
View all changes introduced in this branch ↗︎

[Antreesy]

This I can comprehend 🦭

[miaulalala]

/backport to stable33

[miaulalala]

/backport to stable32