feat: vertical tabs, and Ring as one mono mark (#162)

[Maxaubert]

Closes #162.

What changes

• Tab position (Settings > Appearance, first row): Horizontal, the strip as it was and the default, or Vertical, the tabs as a sidebar down the left.
  • The sidebar uses the existing Tab style: Classic (soft fill and the accent rule on the terminal's side) or Powerline (each row an arrow pointing at the terminal, its edge the mark). No outlined styles.
  • Open: beside the terminal, resized by dragging its right edge (150 to 420 px, kept).
  • Collapsed: takes no room; slides over the terminal while the pointer is at the window's left edge (8 px, 90 ms in, 340 ms grace out). The terminal never resizes, so the shell is not redrawn.
  • Its own button (a sidebar-panel glyph with a chevron) switches the two, and lives only in the sidebar.
  • Rows pick, middle-click close, drag to reorder, take a folder dropped from Explorer, and have the strip's tab menu and + menu.
• Title bar off with vertical tabs: no top row. The bar slides down at the top edge with only command help, Settings and the window buttons (not the app's name), and goes when the pointer leaves. The sidebar's head is the window's handle. Horizontal + title bar off is unchanged (Setting: no title bar (tabs in the top row) #91).
• Ring is now one mono mark by the name for every state, in both layouts: spinner (working), check (finished), breathing dot (question), cross (failed), in the name's own ink, no line or edge. Minimal and Full are unchanged and look the same in both layouts.

Spec and plan: docs/superpowers/specs/2026-10-11-vertical-tabs-design.md, docs/superpowers/plans/2026-10-11-vertical-tabs.md. Mockups: research/prism-terminal/mockups/2026-10-11-vertical-tabs/.

Core change (ships to Prism too)

core/renderer/lib/tabMark.ts and components/TabMark.tsx: Ring's rule and drawing. Prism's strip does not offer Ring (its tabMarks leaves it out), so Prism draws nothing new. Also a new sidebar settings icon and the Ring subtext. Core 0.32.1 -> 0.33.0.

Structure

TabStrip's mark reading and menus are lifted into components/tabLooks.ts and components/tabMenus.tsx (behaviour unchanged), so the strip and the sidebar cannot mark a tab differently. New: TabSidebar.tsx, HoverTitleBar.tsx, lib/hoverReveal.ts (timing as a testable controller), lib/tabLayoutPrefs.ts, lib/sidebarPrefs.ts.

Not in this PR

• The sidebar on the right side (Vertical tab sidebar: pinned or compact (shows at the screen edge) #162 lists it; not asked for in this round).
• A key to toggle the sidebar: Ctrl+B is Claude Code's own.

Checks

• typecheck OK; lint 12 warnings, all pre-existing; unit 1898/1898.
• npm run e2e: all scenarios pass except linkPaintStall's "the path tab A printed wears the link colour", which is flaky on main too (main: 1 fail in 4 runs; this branch: 2 in 4). Not this change.
• New verticalTabs e2e (35 checks): layout, marks in Classic and Powerline under Ring, Minimal and Full, pick, drag reorder, collapse and edge reveal with the terminal unmoved, hidden title bar at the top edge. indicatorStyles now holds the mono Ring on the strip.

App 0.38.1 -> 0.39.0.

🤖 Generated with Claude Code

https://claude.ai/code/session_017XYVRPzvhLpPCr75uB6uaA