fix: resolve all ESLint errors blocking CI releases

- Extract ThemeContext and ToolCollapseContext definitions into separate
  files to satisfy react-refresh/only-export-components rule
- Move useTheme and useToolCollapse hooks to dedicated hook files
- Fix empty catch block in ThemeContext (add comment)
- Replace Date.now() ref in ThinkingIndicator with useState initializer
- Update all imports across components

Closes feedback #58

src/contexts/ThemeContextDef.ts

@@ -0,0 +1,18 @@
+import { createContext } from 'react';
+
+export type ThemeName = 'dark' | 'light' | 'oled';
+export type AccentColor = 'cyan' | 'violet' | 'emerald' | 'amber' | 'rose' | 'blue';
+
+export interface ThemeContextValue {
+  theme: ThemeName;
+  accent: AccentColor;
+  setTheme: (t: ThemeName) => void;
+  setAccent: (a: AccentColor) => void;
+}
+
+export const ThemeContext = createContext<ThemeContextValue>({
+  theme: 'dark',
+  accent: 'cyan',
+  setTheme: () => {},
+  setAccent: () => {},
+});