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-dark.json

@@ -30,7 +30,7 @@
       "subtle": "#292828"
     },
     "interactive": {
-      "border": "#393939",
+      "border": "#2d2c2c",
       "borderHover": "#4C4C4C",
       "borderFocus": "#4589FF",
       "selection": "#ffffff20",