Feature: colour usage bars by level (thresholds per widget)

Feature request: colour a usage bar by its level (thresholds)

Today every widget renders in one fixed color. For the quota widgets (session-usage, weekly-usage, weekly-opus-usage, fable-weekly-usage, context-bar) the number that matters is how full the bar is, and a fixed colour cannot say that: with a calm palette a 20 percent bar and a 92 percent bar look identical except for the fill; with a warm palette every bar looks like a warning all day.

Proposal: optional per-widget thresholds that pick the colour by the current percentage.

{
  "type": "weekly-usage",
  "color": "hex:88C0D0",
  "metadata": {
    "display": "slider",
    "levels": [
      { "from": 0,  "color": "hex:88C0D0" },
      { "from": 70, "color": "hex:EBCB8B" },
      { "from": 90, "color": "hex:BF616A" }
    ]
  }
}

• levels is optional; when absent, behaviour is unchanged.
• The last matching from wins; the colour applies to the bar, its percentage text and any merged label.
• Same shape would work for context-percentage / context-bar (where "used" is the level) and for block-timer (time remaining inverted).

Editor support could be a "Levels" sub-menu on those widgets, but the JSON field alone would already cover scripted setups.

Happy to test a build. Thanks for the tool, the slider widgets and the merge flag are what make a two-line layout readable.