feat(theme): add OpenChamber hybrid theme and make it the default

- Add OpenChamber brand theme (dark+light): Vitesse syntax over OpenCode-deep neutrals with Flexoki accents, harmonized in OKLCH

- Add scripts/harmonize-theme.mjs: align accent saturation/lightness and boost syntax chroma via OKLCH

- Set default theme to OpenChamber (was Flexoki)

- Rename fields-of-the-shire off the openchamber-* id; keep it as a normal preset

- Remove OpenCode and OC-2 ports and all disabled theme JSON definitions

- Make panel/header/sidebar borders opaque and theme-driven; global default border now uses --border instead of hardcoded rgba

packages/ui/src/lib/theme/themes/carbonfox-light.json

@@ -27,10 +27,10 @@
       "elevated": "#f4f4f7",
       "elevatedForeground": "#161616",
       "overlay": "#00000020",
-      "subtle": "#f2f2f8"
+      "subtle": "#f6f6f8"
     },
     "interactive": {
-      "border": "#DCDCDC",
+      "border": "#e3e2e2",
       "borderHover": "#D0D0D0",
       "borderFocus": "#0F62FE",
       "selection": "#cacfd87f",