feat(map-editor): menu-bar top-level labels render + click

Adds the seven category labels (File, Edit, View, Map, Tools,
Window, Help) at the top of the screen with hover highlight and
click-to-open / click-to-close behaviour. Item arrays are still
empty stubs; dropdown rendering lands in the next slice.

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

init.lua

@@ -445,6 +445,25 @@ local ui = (function()
         "topsurface", "surface", "subsurface", "foundation",
     }
 
+    -- Item-array stubs for the dropdown system. Filled in T9.
+    local FILE_ITEMS   = {}
+    local EDIT_ITEMS   = {}
+    local VIEW_ITEMS   = {}
+    local MAP_ITEMS    = {}
+    local TOOLS_ITEMS  = {}
+    local WINDOW_ITEMS = {}
+    local HELP_ITEMS   = {}
+
+    local MENU_CATEGORIES = {
+        { name = "File",   items = FILE_ITEMS   },
+        { name = "Edit",   items = EDIT_ITEMS   },
+        { name = "View",   items = VIEW_ITEMS   },
+        { name = "Map",    items = MAP_ITEMS    },
+        { name = "Tools",  items = TOOLS_ITEMS  },
+        { name = "Window", items = WINDOW_ITEMS },
+        { name = "Help",   items = HELP_ITEMS   },
+    }
+
     -- Top-toolbar buttons (left-to-right). Action ids dispatched in
     -- handle_click; hotkey labels rendered on the button face.
     local TOOLBAR_BUTTONS = {
@@ -570,6 +589,45 @@ local ui = (function()
         end
     end
 
+    -- Returns the hit-rect table for each menu-bar category label.
+    -- Uses engine.render.measure_text (exposed in P.3.4).
+    local function menu_bar_categories_layout()
+        local out = {}
+        local x = MENU_LABEL_PAD_X
+        local font_size = 12
+        for _, cat in ipairs(MENU_CATEGORIES) do
+            local label_w = engine.render.measure_text(cat.name, font_size)
+            local hit_w = label_w + MENU_LABEL_PAD_X * 2
+            out[#out + 1] = {
+                name    = cat.name,
+                items   = cat.items,
+                x       = x,
+                y       = 0,
+                w       = hit_w,
+                h       = MENU_BAR_H,
+                label_x = x + MENU_LABEL_PAD_X,
+            }
+            x = x + hit_w
+        end
+        return out
+    end
+
+    local function draw_menu_bar(mx, my)
+        local screen_w = engine.window.size()
+        engine.render.draw_rect(0, 0, screen_w, MENU_BAR_H, rgba(COL_TOOLBAR_BG, 0xFF))
+        local open = state.get_menu_open()
+        for _, cat in ipairs(menu_bar_categories_layout()) do
+            local hovered = in_rect(mx, my, cat.x, cat.y, cat.w, cat.h)
+            local active = (open == cat.name)
+            if active or hovered then
+                engine.render.draw_rect(cat.x, cat.y, cat.w, cat.h,
+                    rgba(active and COL_BUTTON_BG_ACTIVE or COL_BUTTON_BG_HOVER, 0xFF))
+            end
+            local fg = active and COL_TEXT_ACTIVE or COL_TEXT
+            engine.render.draw_text(cat.name, cat.label_x, 5, 12, rgba(fg, 0xFF))
+        end
+    end
+
     local function side_panel_layout()
         local screen_w, screen_h = engine.window.size()
         return {
@@ -825,6 +883,7 @@ local ui = (function()
 
     function M.draw()
         local mx, my = engine.input.get_mouse_pos()
+        draw_menu_bar(mx, my)
         draw_top_toolbar(mx, my)
         draw_mode_pill()
         draw_side_panel(mx, my)
@@ -948,6 +1007,26 @@ local ui = (function()
             end
         end
 
+        -- Menu bar top-level labels
+        for _, cat in ipairs(menu_bar_categories_layout()) do
+            if in_rect(mx, my, cat.x, cat.y, cat.w, cat.h) then
+                if button == "left" then
+                    if state.get_menu_open() == cat.name then
+                        state.close_menu()
+                    else
+                        state.set_menu_open(cat.name)
+                    end
+                end
+                return true
+            end
+        end
+
+        -- Click anywhere outside the menu bar closes any open dropdown
+        if state.get_menu_open() and my >= MENU_BAR_H then
+            state.close_menu()
+            -- Fall through (do not return) so the click can hit something else.
+        end
+
         -- Top toolbar buttons
         for _, b in ipairs(toolbar_buttons_layout()) do
             if in_rect(mx, my, b.x, b.y, b.w, b.h) then