feat: vertical tabs, finished: a bar across the top, find a tab, one line round the terminal, acrylic sidebar, fixed tabs

[Maxaubert]

Follow-up to #190 (#162), from the owner on 2026-10-11: "the title bar disappears too easily, my cursor can be on the titlebar and its disappearing ... i should be able to have the cursor 2-3 px off the titlebar before it disappears ... sidebar is also somewhat broken, if i have the cursor on the sidebar at the top of it it will disappear when im still on the sidebar. lower down though it works fine".

Cause

The dropped bar and the sidebar's grab strip are drag regions: a press there is Windows', so the page hears no pointer move over them, and Windows tells the page the pointer has left. So the bar went away with the cursor on it, and the sidebar went away at its top (the grab strip) but not lower down (the tabs, which are the page's).

Fix

• Main streams the cursor (content-relative, 50 ms, only while the bar or a collapsed sidebar can show), not just "at the edge".
• One rule, lib/revealZones.ts, decides from main's cursor or the page's pointer: in at the edge zone (top 16 px, left 24 px), out only past the far edge plus 4 px (the bar's bottom, the sidebar's right edge), with the existing 340 ms grace.
• Under --e2e only, main reads the suite's cursor (globalThis.__e2eCursor), never the owner's.

App only. 0.39.6 -> 0.39.7.

Checks

• New e2e checks, failing first: with main's cursor on the bar, then 3 px below it, and on the sidebar's top strip, then 3 px past its edge, while the page is told the pointer left: 4 FAIL on the old code, pass now; both go once the cursor is clearly off them.
• New unit tests for the rule (revealZones.test.ts); unit 1907/1907 total; typecheck and lint clean. verticalTabs 53/53.

Added on 2026-10-12, before merging (installed for the owner first)

• The bar starts at the sidebar's on-screen edge, a slid-out collapsed one included ("not overlay over the sidebar"); it spans the window only with no sidebar showing.
• No line under the pop-out bar.
• Secondary colour, a new Appearance setting under Background and Accent: the vertical tabs' sidebar, pop-out bar and shown title bar wear it. Unpicked it is the theme's flat panel (--p-secondary, the ground 4 percent toward the text), the owner's pick from the surfaces mockup on every theme; a pick is held to the ink floors; a theme pick resets it. Snapshots change only by the new token.
• New tab is the tab list's last row, a tab's size; the foot keeps Help, Settings and the sidebar button.
• A 16 px grab strip above the tabs (10 px was Windows' resize border, WM_NCHITTEST answered HTTOP).
• Under Ring, a tab with no mark keeps the slot, so names line up.
• e2e verticalTabs 57/57, indicatorStyles, titleBar, options, themeSwitch pass; unit 1948/1948. App 0.39.8.

🤖 Generated with Claude Code

https://claude.ai/code/session_017XYVRPzvhLpPCr75uB6uaA