Offline mode banner overlaps the navigation title and hides toolbar actions (missing on visionOS) #415

Problem

Seen in TestFlight 1.8.0 (1541) on iPhone. When Labstream cold-launches into the restricted Offline surface (#259), the "Offline mode" banner is pinned to the top of the screen and covers the navigation bar:

• The large Offline title is clipped to its bottom half on the first frame.
• The navigation bar's Sign In and Settings toolbar buttons are hidden behind the banner on iPhone and iPad, so the only ways to sign in again or open Settings are not visible.
• The secondary line ("Your server could not be reached. Completed downloads remain available.") wraps onto 2–3 lines on iPhone. At accessibility text sizes the banner fills about 40% of the screen and "Reconnect" hyphenates to "Recon-/nect".

Root cause

Labstream/Shared/UI/OfflineLaunchView.swift mounts offlineStatusBanner with .safeAreaInset(edge: .top) outside the NavigationStack. On iOS/iPadOS the inset is added above the stack's content, but the navigation bar still lays out at the top of the window, so the banner (.regularMaterial) sits on top of the bar's inline row and the top of the large title. The banner is also a separate, one-off status pattern: OfflineLibraryView already shows inline notice rows (startup-recovery "Retry Recovery", upgrade notice "Dismiss") in a different layout.

Per-platform findings

Reproduced headlessly with a local DEBUG-only --ui-testing --ui-testing-fixture offline launch, which mounts OfflineLaunchView directly with no server. Screenshots are kept locally (gitignored artifacts/agent-sim-runs/offline-banner/) and are not uploaded.

Proposed direction

Replace the free-floating top inset with a platform-native status treatment that never overlaps navigation chrome:

1. Keep the offline state inside the navigation hierarchy, either as a navigation subtitle plus a toolbar Reconnect action, or as the first row of the Offline list using the same notice-row pattern as the existing recovery/upgrade notices. Do not inset it outside the NavigationStack.
2. Shorten the copy to a context line that never wraps (for example "Server unreachable"). The longer explanation can go in the accessibility label or a details affordance.
3. Make it visible on visionOS (it is currently missing) and confirm macOS.
4. Have one notice-row pattern shared by offline / startup-recovery / upgrade-notice states, so color and button style carry one meaning each.

HTML mockups of 2–3 options are being reviewed before implementation.

Acceptance

• iPhone (default and AX text sizes): no overlap with title or toolbar; Sign In and Settings reachable.
• iPad: same.
• visionOS: offline state and Reconnect visible.
• macOS: verified on an unlocked host via scripts/deploy-macos-to-host.sh.
• tvOS unaffected (no Offline surface).
• A DEBUG offline UI fixture is kept so this surface can be screenshot-tested headlessly.