v1.1.1 — export and overlay fixes

Bug fixes from the first round of downstream reports, plus two Apple platform bugs found and documented along the way.

Exports that silently lost work now keep it, or fail loudly

• Clips without audio keep their edits (#201, thanks @timehzy in #204). An empty audio track made the HEVC preset reject the composition, and the export fell back to a passthrough copy of the first clip, reporting success.
• No more silent passthrough. If a preset still can't encode a composition, the export now throws KadrError.exportFailed instead of dropping transitions, track layout, crop or overlays.

Multi-track

• Parallel tracks draw over the main chain (#205). AVFoundation reads the first layer instruction as the top layer; Kadr emitted them the other way round, so overlays were hidden. Visible change: compositions that relied on the old order will now show their overlays, as documented.
• A track that ends early stops rendering (#206) instead of holding its last frame, on both the default compositor and a custom MultiInputCompositor.

Overlays

• TextOverlay renders in macOS exports (#202).
• Overlay exports no longer turn white at some sizes (e.g. 320×320, 560×560, 640×320). An AVFoundation bug, worked around invisibly.
• iOS Simulator: exports with overlays now throw instead of crashing the app. An Apple bug in the iOS 26.5 / 27.0 Simulators kills the process; devices and macOS are unaffected.

Documentation

• New Known Platform Issues article: the Simulator overlay crash, and transition previews stalling on the iOS 26 Simulator (#203). Each has symptom, cause and workaround.

683 tests, passing on macOS and on the iOS 26.5 Simulator. Source-compatible; no API changes.