feat: Workspace tabs + splits + agent launcher (v7.8.0)

[vakovalskii]

What

Turns the single-pane terminal into an iTerm-like workspace:

• Named tabs — double-click to rename; + to add, × to close.
• Splits — each tab splits into 1–4 panes (layout buttons or + Pane); every pane is an independent xterm + WebSocket + server-side pty.
• Agent launcher — a per-pane Launch ▾ dropdown types an agent command (Claude Code / Codex / Qwen / OpenCode / Kiro / Gemini) straight into that pane's shell.
• Background tabs stay alive — each tab keeps its own hidden grid, so switching tabs never kills a running shell; only the active grid is shown.

How

• Model: _wsTabs = [{ id, name, panes:[{id,cmd,term,sock,fit,ro}] }] + _wsActiveTabId.
• Panes reconcile incrementally (append/remove DOM, no innerHTML rebuild), so live panes are never torn down when adding/removing others.
• A ResizeObserver per pane refits xterm + notifies the pty ({t:'resize'}) on any layout/window/tab change.
• renderWorkspace is idempotent — background dashboard refreshes (active-session poll, session reload) call render() while on this view and must not reset the terminal.
• No server changes — the server already spawns one pty per /ws/terminal connection.

Testing

• Full suite: 166 pass, 2 skipped (win32), 0 fail.
• Browser: 2 tabs with 2- and 3-pane layouts → 5 live ptys; distinct shells; rename works; switching to a background tab and back keeps its panes/ptys alive.

Next (per docs/SUPERAPP_PLAN.md)

WebGL renderer + context-loss fallback, drag-resize pane borders, tmux-less persistence (pty-host + serialize/replay so tabs/panes survive reload), saved commands & per-project cwd, proxy.

Version

Minor bump 7.7.0 → 7.8.0.

🤖 Generated with Claude Code