feat(console): toolbar toggle to hide per-line color accent bars

Adds a paint-bucket toggle button to the console toolbar (in the appearance
cluster next to zoom) that shows/hides the per-line left color accent bars for
a cleaner monochrome gutter. The icon reflects state (FORMAT_COLOR_FILL when on,
a dimmed FORMAT_COLOR_RESET when off) with a tooltip. Session-only, like the
console zoom factor; default on.

Adds console_toggle_accents to the English source and all eight translations
(no new CJK glyphs — the subset font already covers them).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

res/lang/zh.json

@@ -240,6 +240,7 @@
     "console_status_stopping": "停止中",
     "console_status_unknown": "未知",
     "console_tab_completion": "Tab 补全",
+    "console_toggle_accents": "切换行颜色强调",
     "console_type_help": "输入 'help' 查看可用命令",
     "console_welcome": "欢迎使用 ObsidianDragon 控制台",
     "console_zoom_in": "放大",