patch to fix undo/redo and erase with layers

Layer controls! import SVGs from Bantam Tools Studio Image converter

Corrected some bugs that could cause lines to disappear and reappear

Changes since 6.4 : Performance & Stability - Launch optimization: Application now responds to touches in 50ms (10-40× faster) through background migrations and deferred initialization - Asynchronous path loading: Prevents UI freezing with large drawings (4000+ paths) - Drawing order fix: New strokes properly appear on top of existing strokes - Memory optimization: Eliminated expensive document.paths access during undo/redo - Fine-grained persistence: Each path stored as separate SwiftData entity for faster saves - Background saves: Debounced saves use background context with actor pattern to avoid main-thread stalls - Pre-rendered thumbnails: Instant document list rendering with cached PNG thumbnails - Batch processing migrations: SwiftData migrations process in 100-entity batches to prevent memory issues Rendering System Overhaul - Triangle-based tessellation: Replaced circles-and-rectangles with non-overlapping triangle meshes for semi-transparent paths - LibTessSwift integration: Production-grade polygon tessellation with automatic hole support - Clipper2 integration: Industry-standard path offsetting and contour extraction for accurate stroke generation - Multi-hole support: Correctly renders paths with 3-4+ self-intersecting loops - Robust stroke rendering: Eliminates spikes, orientation errors, and over-brightening artifacts on overlaps - Standard alpha blending: Proper premultiplied alpha (source-over) with transparent clear - Hybrid rendering system: Metal for completed paths (4× MSAA), Core Graphics for live drawing - LRU tessellation cache: 500MB cache with geometry hashing for instant re-renders Drawing Experience Enhancements - Vector eraser polish: Reliable partial erases with geometry rebuild and polygon-based intersection - Extended line width range: Now 0.01-10mm with quick preset buttons (0.5, 0.7, 1.0, 2.0, 5.0mm) - Improved palette UX: Add button always visible, semi-transparent colors hidden in public builds - Reference image optimization: Preserves quality, only downsamples when exceeding 300 DPI canvas resolution - Improved path processing: Conservative supersample algorithm preserves shape character Technical Infrastructure - Migration safety: UserDefaults flags prevent redundant work, failed migrations retry on next launch - Silent failure handling: Non-critical operations fail gracefully without crashes or logging spam - Detached low-priority tasks: Background operations use .utility priority to avoid UI blocking - Clipper2-based routing: Automatic hole detection for nearly-closed loops (checks contour count, not just threshold) - Parallel tessellation: Batch tessellation for large drawings with efficient cache invalidation Bug Fixes - Fixed race condition crash: In async path processing - Fixed import duplication: SVG paths no longer duplicate on import - Fixed undo/redo lag: Eliminated expensive array rebuilds - Fixed path ordering: New entities correctly use fractional ordering for stable sort - Fixed closed path detection: Now routes to LibTess based on Clipper2 contour count rather than distance threshold - Fixed color equality tests: Resolved SwiftUI color space comparison issues

Version 6.4 - added import function that will allow you to import svgs exported with version 6.2 or later

Version 6.3 Release notes: - Visual UI bug resolved when using zoom accessibility on iphones - minimum IOS version now 18, changes to swiftdata caused issues with IOS 17 compatibility - fix bug where path simplification not being respected

version 6.1 Release notes: - Updated touch based drawing to be more responsive by making it so touches are assumed to be drawing and will cancel if a gesture is detected. - Color window on Iphone now opens fully - Fixed undo bug that caused lines to disappear and reappear