fix(ios): constrain releaseCapture to direct temporary files

[OskarEichler]

Summary

Constrain releaseCapture to regular files that are direct children of React Native's temporary directory.

The implementation replaces raw string-prefix recursive removal with exact-root/direct-child validation and descriptor-relative, nonrecursive deletion. It rejects traversal, prefix siblings, directories, NULs, and symbolic-link escapes while preserving raw paths returned by RCTTempFilePath.

The native regression test now verifies that a file in a prefix-only sibling such as ReactNativeImposter is preserved.

Compatibility

Normal native-generated capture paths continue to release correctly. Arbitrary paths that merely share the temporary-root prefix, nested paths, directories, and symbolic links are no longer removed. No dependency or SDK version changes.

Verification

• Focused iOS Simulator XCTest target: 5 tests passed, 0 failures
• The targeted test covers normal capture deletion, missing files, outside paths, the root directory itself, and prefix-only sibling paths
• git diff --check

Type: fix

[OskarEichler]

Resolved the draft blocker by updating the existing native regression to assert the fixed behavior: prefix-only sibling paths are preserved. I reran the focused iOS Simulator XCTest target against the actual CocoaPods workspace; all 5 RNViewShotReleaseCaptureTests pass with 0 failures. I’ve marked the PR ready for review.