ios: wait for the limited attachment grid in its hosted test - #2016

Test-only fix-forward

Wait for the limited-access attachment grid to be visible and contain its seven items before unwrapping it. This moves the existing 10-second condition wait ahead of the unwrap; it does not increase the budget. All grid-count, limited-access note, Manage control and camera geometry assertions remain.

The shared menu() helper waits for presentation and then pauses for 600 ms, which does not establish that the actual grid is ready on a busy runner. This PR changes only the affected test, not app behavior or other test expectations.

History and causality

• Post-ios: label Cloud tool calls with their display summaries #2015 main 6c8758d62: this test failed at line 254 because the grid lookup was nil (job 128934487181).
• Pre-ios: label Cloud tool calls with their display summaries #2015 main 7b37e8efb: the same test passed, in 0.836 seconds (job 128927343478). No earlier occurrence was found in the retained logs.
• The fixed-delay readiness heuristic predates ios: label Cloud tool calls with their display summaries #2015, but a pre-existing failure is not proven. This is a narrow synchronization correction, not a claim that an earlier failing baseline was reproduced.

Verification

• Exact test: 20 consecutive passes, no retries, on Kirill Mac's iOS 27 simulator with CI's 2.5 time scale.
• Evidence: /Users/kirilldubovitskiy/ctb-out/attach-readiness.kXmFLt/repeated.xcresult (20 tests, zero failures).
• Full HostedAttachMenuTests class: 12/12 passed, same directory's suite.xcresult.
• Independent exact-commit source review: PASS, no findings.

Intentionally left unmerged for coordinator review. BrowserStates/proxy investigation is separate; no browser code, assertion weakening, Preview upload, or infrastructure change is included.