feat(map-editor): layout constants for menu-bar UI

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

init.lua

@@ -334,6 +334,23 @@ local ui = (function()
     -- =====================================================================
     -- Layout constants
     -- =====================================================================
+    -- Menu bar (replaces TOOLBAR_H block in v0.3.0)
+    local MENU_BAR_H           = 24
+    local MENU_LABEL_PAD_X     = 12
+    local MODE_PILL_W          = 130
+    local MODE_PILL_H          = 18
+    local MODE_PILL_SEG_W      = 65
+    local MODE_PILL_MARGIN     = 4
+
+    -- Dropdown
+    local DROPDOWN_PAD_Y       = 4
+    local DROPDOWN_ITEM_H      = 22
+    local DROPDOWN_INDICATOR_W = 18
+    local DROPDOWN_HOTKEY_W    = 60
+    local DROPDOWN_BORDER      = 1
+    local DROPDOWN_MIN_W       = 180
+    local DROPDOWN_PAD_X       = 10
+
     -- Top toolbar (full-width, mode-switch + action buttons)
     local TOOLBAR_H            = 32
     local TOOLBAR_BUTTON_W     = 88
@@ -387,6 +404,8 @@ local ui = (function()
     local COL_VERTEX_GRID      = 0xFFFFFF
     local COL_VERTEX_DOT       = 0xFFB040
     local COL_VERTEX_SNAP      = 0x40FF60
+    local COL_CHECK            = 0x60E060
+    local COL_TEXT_DISABLED    = 0x606068
 
     -- HSV-derived swatch colors (one per slot, 1..14). Pre-computed so
     -- the palette has visually distinct previews while real tile