Stabilize iPad system UI actions

[jacklv-coder]

Summary

• retry iPad file/folder creation menu actions through freshly validated physical frames
• re-query document-picker destinations and dispatch only through captured App coordinates
• present UIActivityViewController from a UIKit presenter as a real iPad popover, with automatic compact-width adaptation on iPhone
• defer temporary export cleanup until the activity completes so Save to Files can consume the URL
• add a self-contained export UI smoke that verifies Save to Files actually opens the document picker without depending on document import
• retain accessibility hierarchy/frame evidence and refresh bilingual changelogs plus reproducible compliance evidence

Verification

• swift test — 200 tests, 0 failures (1 expected environment-dependent skip)
• pinned RootFS archive size/SHA-256 — passed
• targeted iPad file creation and iPhone/iPad iOS 18.0 system-file round trips — passed
• dedicated file-export/document-picker handoff — passed on iPad 10th generation / iOS 18.2
• dedicated file-export/document-picker handoff — passed on iPhone 16 / iOS 18.2
• runtime smoke script tests — passed
• release compliance tests — 71 runs / 679 assertions
• bilingual documentation and reproducibility checks — passed
• Codex CR after final diff — no actionable correctness issues