fix(bubble): provider-tinted bar fill, tighten countdown gap

Two visible regressions from the previous pass:

1. Codex bars still rendered orange even though the accent stripe was
   white — `ring_color_for_percent` only knew the percentage, not the
   provider, so it returned the Claude-style orange/amber/red ramp for
   both models. Replaced with `bar_fill_color(model, is_dark, pct)`:

   - <60%   → accent_color_for(model, is_dark)  (Claude orange / Codex
              white-on-dark / Codex charcoal-on-light)
   - 60-80% → amber  (#E0A040)
   - 80-95% → red    (#C45020)
   - ≥95%   → deep red (#A01818)

   Alarm bands stay model-agnostic so an approaching limit always looks
   the same. The "safe" band carries the provider's identity. Mirrored
   into the panel via `bar_color_for(model, percent, is_dark)`.

2. Big visible gap between bar end and countdown text — the column
   was sized for the old combined "100% · 23h" probe string (~9 chars)
   but the bubble now renders countdown-only (~3 chars). Probe template
   shrunk to "999d" so the right column is no longer ~70 px reserved
   for ~14 px of text. Countdown also flipped from DT_RIGHT to DT_LEFT
   so "3h" / "19h" sit immediately next to the bar with just the
   `label_pad` gap, instead of floating at the bubble's far edge.

Inline-percent contrast calc uses `bar_fill_color` so the
luminance-based foreground colour responds to the new white/charcoal
Codex bars (black-on-white in safe band, white-on-amber/red in alarm).

Side effect: `ring_color_for_percent` is gone — it had no internal
callers outside the two replaced sites. `bar_fill_color` is now the
only public bar-color helper.

src/panel.rs

@@ -269,7 +269,7 @@ fn paint(hwnd: HWND, hdc: HDC) {
     } else {
         Color::from_hex("#D6D6D6")
     };
-    let accent = bar_color_for(data.session_pct.max(data.weekly_pct), data.is_dark);
+    let accent = bar_color_for(data.model, data.session_pct.max(data.weekly_pct), data.is_dark);
 
     unsafe {
         let bg_brush = CreateSolidBrush(COLORREF(bg.into_colorref()));
@@ -482,8 +482,8 @@ fn draw_text(
     }
 }
 
-fn bar_color_for(percent: f64, _is_dark: bool) -> Color {
-    crate::bubble::ring_color_for_percent(percent)
+fn bar_color_for(model: ProviderId, percent: f64, is_dark: bool) -> Color {
+    crate::bubble::bar_fill_color(model, is_dark, percent)
 }
 
 fn clone_data() -> Option<PanelData> {