polish(v0.6): replace toolbar emoji with themed line icons + hover tooltips

The glossy emoji (🔍⚙▦🕘⌨🔗📱) clashed with the Amber dark theme. Swap them
for clean lucide line icons (MIT, stroke=currentColor) so they take the theme
colour — muted by default, Amber on hover — and add a styled CSS hover tooltip
(data-tip, right-anchored so it never clips the edge) showing what each does.

- public/icons.ts: 7 line icons (search/settings/dashboard/history/keyboard/
  share/device), script-generated from lucide
- 7 toolbar modules: innerHTML = ICON_* + data-tip + aria-label
- style.css .toolbtn: 18px svg, --text-dim → --accent on hover, [data-tip] tooltip

Frontend-only. web typecheck + build clean; bundle has 0 toolbar emoji; verified
in-browser: line icons in theme colour, amber + tooltip on hover.

public/history.ts

@@ -6,6 +6,8 @@
  * `claude --resume <id>`.
  */
 
+import { ICON_HISTORY } from './icons.js'
+
 export interface HistoryHooks {
   resume: (cwd: string, id: string) => void
 }
@@ -98,8 +100,9 @@ export function mountHistory(toolbar: HTMLElement, hooks: HistoryHooks): void {
 
   const toggle = document.createElement('button')
   toggle.className = 'toolbtn'
-  toggle.textContent = '🕘'
-  toggle.title = 'Resume a past Claude session'
+  toggle.innerHTML = ICON_HISTORY
+  toggle.dataset.tip = 'Session history'
+  toggle.setAttribute('aria-label', 'Session history')
   toggle.setAttribute('aria-label', 'Session history')
   toggle.addEventListener('click', () => {
     if (overlay.style.display === 'none') void open()