Sidebar + theme: drop hamburger cycle no-op branch; add brandMixTo CSS var to themes for logo-gradient end color

static/js/theme.js

@@ -26,7 +26,7 @@ export const THEMES = {
   gpt:        { bg:'#212121', fg:'#ececec', panel:'#171717', border:'#424242', red:'#949494',
                 advanced: { sendBtnBg: '#949494', sendBtnHover: '#7f7f7f',
                             userBubbleBg: '#2f2f2f', aiBubbleBg: '#171717',
-                            inputBg: '#2f2f2f' } },
+                            inputBg: '#2f2f2f', brandColor: '#ffffff', brandMixTo: '#ffffff' } },
   claude:     { bg:'#262624', fg:'#f5f4f0', panel:'#30302e', border:'#4a4a47', red:'#c6613f' },
   cute:       { bg:'#fff0f5', fg:'#d4608a', panel:'#fff8fa', border:'#f0c0d0', red:'#ff6b9d' },
 };
@@ -184,6 +184,7 @@ const ADV_KEYS = [
   { key: 'bubbleBorder',       css: '--bubble-border',     label: 'Border Chat Bubble', group: 'Chat Bubbles' },
   { key: 'sidebarBg',          css: '--sidebar-bg',        label: 'Sidebar Bg',       group: 'Sidebar' },
   { key: 'brandColor',         css: '--brand-color',       label: 'Odysseus Logo',    group: 'Sidebar' },
+  { key: 'brandMixTo',         css: '--brand-mix-to',      label: 'Logo Gradient End', group: 'Sidebar' },
   { key: 'hamburgerColor',     css: '--hamburger-color',   label: 'Hamburger Menu',   group: 'Sidebar' },
   { key: 'inputBg',            css: '--input-bg',          label: 'Input Bg',         group: 'Chat Input / Prompt Area' },
   { key: 'inputBorder',        css: '--input-border',      label: 'Input Border',     group: 'Chat Input / Prompt Area' },
@@ -203,6 +204,7 @@ function computeAdvancedDefaults(colors) {
     bubbleBorder: colors.border,
     sidebarBg: colors.panel,
     brandColor: red,
+    brandMixTo: colors.fg,
     hamburgerColor: colors.fg,
     inputBg: colors.panel,
     inputBorder: colors.border,