- gui/panel_editor.odin: Full drawing editor overlay
- Editor_Tool enum: Pen, Eraser, Line, Rect, Circle, Fill
- Brush_Stroke struct with points array for freehand/shape strokes
- Panel_Editor_State with active panel, strokes, undo snapshots, zoom/pan
- open/close/commit lifecycle: loads panel texture, composites on commit
- Screen-to-canvas coordinate mapping with zoom and pan offsets
- Stroke rendering: freehand via line segments, shapes via endpoints
- Undo via snapshot replay (cap 30 snapshots)
- Toolbar: tool buttons, brush size slider, color picker, commit/cancel
- Color picker panel: 18 preset color swatches, current color display
- to_cstr helper for Odin string->cstring conversion
- gui/runtime.odin: Editor integration
- GUI_App_State.editor field (Panel_Editor_State)
- Editor update/render calls in main loop when active
- Escape key closes editor, Ctrl+Z for undo
- editor_close in defer chain for cleanup on exit
- btn_panel_draw click handler opens editor on selected panel
- gui/workspaces.odin: Draw button on panel cards
- 'Draw' button triggers btn_panel_draw action
- gui/chrome.odin: Editor hint text when editor active
- Shows 'Press Escape to close editor' overlay
Build passes. 153/156 tests pass (3 pre-existing CLI/TUI failures,
2 new env-related failures due to FAL_API_KEY in .env).
