Ship out-of-the-box VSCode-style config and sharp rendering defaults

- quilt patch: first-run user init.lua template now writes a tuned
  default config (Dark Modern theme, JetBrains Mono with grayscale AA,
  line-height/indent guides, compact treeview with hover highlight)
- new theme module usr/share/lite-xl/colors/vscode_dark.lua
- default config in /etc/skel/.config/lite-xl/ for new users
- desktop: launch via SDL software renderer with LITE_SCALE=1.5 so text
  renders 1:1 on fractional-scaled Wayland outputs and avoids panfrost
  GPU artifacts
- depend on fonts-jetbrains-mono for the default code font

debian/extra/init.lua

@@ -0,0 +1,70 @@
+-- Lite XL default configuration (shipped via /etc/skel or the first-run
+-- template). This file is yours to edit; it is reloaded automatically on save.
+-- It gives the editor a VSCode-style dark look out of the box.
+
+local core = require "core"
+local common = require "core.common"
+local config = require "core.config"
+local style = require "core.style"
+
+------------------------------ Appearance -------------------------------------
+-- VSCode "Dark Modern" theme (shipped in /usr/share/lite-xl/colors).
+core.reload_module("colors.vscode_dark")
+
+-- Sharp text: grayscale antialiasing with light autohinting renders crisper
+-- than the defaults on high-DPI panels.
+local font_opts = { antialiasing = "grayscale", hinting = "slight", smoothing = true }
+
+-- Bump these for a bigger/smaller UI; ctrl+wheel also zooms live.
+local UI_FONT_SIZE   = 15
+local CODE_FONT_SIZE = 16
+
+style.font = renderer.font.load(DATADIR .. "/fonts/FiraSans-Regular.ttf",
+  UI_FONT_SIZE * SCALE, font_opts)
+style.big_font = style.font:copy(46 * SCALE)
+style.code_font = renderer.font.load(
+  "/usr/share/fonts/truetype/jetbrains-mono/JetBrainsMono-Regular.ttf",
+  CODE_FONT_SIZE * SCALE, font_opts)
+
+------------------------------ Behavior ---------------------------------------
+
+config.line_height = 1.3        -- airy lines, like VSCode's default
+config.indent_size = 4
+config.plugins.lineguide = true -- indent guides, like VSCode
+
+------------------------------ Treeview sidebar -------------------------------
+-- Tighter rows and VSCode-style hover/selection highlight. Method overrides so
+-- the shared style.padding used by the editor margins is untouched.
+
+local TreeView = require "plugins.treeview"
+
+local tv_row_pad = common.round(3 * SCALE)
+function TreeView:get_item_height()
+  return style.font:get_height() + tv_row_pad
+end
+
+local tv_base_indent  = common.round(8 * SCALE)
+local tv_level_indent = common.round(10 * SCALE)
+function TreeView:draw_item(item, active, hovered, x, y, w, h)
+  self:draw_item_background(item, active, hovered, x, y, w, h)
+  x = x + tv_base_indent + item.depth * tv_level_indent
+  x = x + self:draw_item_chevron(item, active, hovered, x, y, w, h)
+  self:draw_item_body(item, active, hovered, x, y, w, h)
+end
+
+function TreeView:get_item_text(item, active, hovered)
+  local color = (active or hovered)
+    and (style.treeview_text_active or style.accent)
+    or  (style.treeview_text or style.text)
+  return item.name, style.font, color
+end
+
+function TreeView:draw_item_background(item, active, hovered, x, y, w, h)
+  if hovered then
+    local c = { table.unpack(style.treeview_hover_bg or style.line_highlight) }
+    c[4] = 160
+    renderer.draw_rect(x, y, w, h, c)
+  elseif active then
+    renderer.draw_rect(x, y, w, h, style.treeview_active_bg or style.line_highlight)
+  end
+end