refactor(debugger): split tile viewer into focused widgets

[mikai233]

Summary

• split the large tile viewer into focused model, geometry, painter, canvas, settings, side panel, control, and tile info widget files
• keep texture lifecycle, backend bridge calls, and state orchestration in tile_viewer.dart
• avoid Dart part files

Verification

• dart format apps/nesium_flutter/lib/features/debugger/tile_viewer.dart apps/nesium_flutter/lib/features/debugger/tile
• flutter analyze
• git diff --check -- apps/nesium_flutter/lib/features/debugger/tile_viewer.dart apps/nesium_flutter/lib/features/debugger/tile