feat(v0.3): O2 — resume past Claude sessions

- src/http/history.ts: listSessions() reads ~/.claude/projects/*/*.jsonl
  (mtime-sorted, top 50), parseSessionMeta() extracts cwd + first user prompt
  (pure, 4 unit tests); GET /sessions
- terminal-session: opts.initialInput (typed ~700ms after the shell is ready)
- tabs.newTabForResume(cwd,id): new tab in the project dir running
  'claude --resume <id>'
- public/history.ts: 🕘 panel listing sessions (project · time · preview) with
  Resume buttons
- Verified: /sessions returns 44 real sessions; panel lists project/time/preview.
  216 tests green.

public/history.ts

@@ -0,0 +1,109 @@
+/**
+ * public/history.ts — resume a past Claude Code session (O2).
+ *
+ * A 🕘 toolbar button opens a list of past sessions (GET /sessions); clicking
+ * "Resume" opens a new tab in that project's directory and runs
+ * `claude --resume <id>`.
+ */
+
+export interface HistoryHooks {
+  resume: (cwd: string, id: string) => void
+}
+
+interface HistorySession {
+  id: string
+  cwd: string
+  project: string
+  mtimeMs: number
+  preview: string
+}
+
+function relTime(ms: number): string {
+  const s = Math.max(0, (Date.now() - ms) / 1000)
+  if (s < 60) return 'just now'
+  if (s < 3600) return `${Math.floor(s / 60)}m ago`
+  if (s < 86400) return `${Math.floor(s / 3600)}h ago`
+  return `${Math.floor(s / 86400)}d ago`
+}
+
+export function mountHistory(toolbar: HTMLElement, hooks: HistoryHooks): void {
+  const overlay = document.createElement('div')
+  overlay.id = 'historymodal'
+  overlay.style.display = 'none'
+  const card = document.createElement('div')
+  card.className = 'hist-card'
+  overlay.appendChild(card)
+  document.body.appendChild(overlay)
+
+  const hide = (): void => {
+    overlay.style.display = 'none'
+  }
+  overlay.addEventListener('click', (e) => {
+    if (e.target === overlay) hide()
+  })
+
+  const open = async (): Promise<void> => {
+    card.replaceChildren()
+    const title = document.createElement('div')
+    title.className = 'hist-title'
+    title.textContent = 'Resume a Claude session'
+    card.appendChild(title)
+    const status = document.createElement('div')
+    status.className = 'hist-empty'
+    status.textContent = 'Loading…'
+    card.appendChild(status)
+    overlay.style.display = 'flex'
+
+    let sessions: HistorySession[]
+    try {
+      const res = await fetch('/sessions')
+      sessions = (await res.json()) as HistorySession[]
+    } catch {
+      status.textContent = 'Failed to load sessions.'
+      return
+    }
+    if (sessions.length === 0) {
+      status.textContent = 'No past Claude sessions found.'
+      return
+    }
+    status.remove()
+
+    for (const s of sessions) {
+      const row = document.createElement('div')
+      row.className = 'hist-row'
+
+      const main = document.createElement('div')
+      main.className = 'hist-main'
+      const proj = document.createElement('div')
+      proj.className = 'hist-proj'
+      proj.textContent = `${s.project}  ·  ${relTime(s.mtimeMs)}`
+      const prev = document.createElement('div')
+      prev.className = 'hist-prev'
+      prev.textContent = s.preview || '(no preview)'
+      prev.title = s.cwd
+      main.append(proj, prev)
+
+      const btn = document.createElement('button')
+      btn.className = 'hist-resume'
+      btn.textContent = 'Resume'
+      btn.addEventListener('click', () => {
+        hooks.resume(s.cwd, s.id)
+        hide()
+      })
+
+      row.append(main, btn)
+      card.appendChild(row)
+    }
+  }
+
+  const toggle = document.createElement('button')
+  toggle.className = 'toolbtn'
+  toggle.textContent = '🕘'
+  toggle.title = 'Resume a past Claude session'
+  toggle.setAttribute('aria-label', 'Session history')
+  toggle.addEventListener('click', () => {
+    if (overlay.style.display === 'none') void open()
+    else hide()
+  })
+  toolbar.appendChild(toggle)
+}