What Problem This Solves

The desktop Control UI spent a ~258px column on chrome: brand row, pinned nav, a "More" tree, New session, the session list, and a footer icon row. The chrome cost is worst in chat split view, which is exactly where horizontal space matters. Two adjacent defects in the same surface: the collapsed session-workspace strip rendered a document glyph styled like a button that did nothing (a bare span, aria-hidden, no handler), and the workspace rail was hard-fixed to the pane's right edge even though the terminal panel already demonstrates right/bottom docking.

Fixes #103420.

Why This Change Was Made

Requested by the maintainer: move the sidebar's buttons into a top bar, make the layout calmer, fix the dead second button in the pane strip, and make the per-session panel dockable/draggable inside its session pane ("the sidebar is attached to the selection", like the terminal's right/bottom dock).

Design decisions:

• Topbar owns app chrome. Brand (with the connection dot riding on the logo), Chat + pinned route pills, a More menu (unpinned routes, plugin tabs, Docs, pin editor), the command-palette search pill, pairing, theme toggle, and Settings. The left column becomes a sessions-only panel; Cmd+B now hides it completely and the 78px icon rail is deleted (navigation no longer needs a rail fallback).
• Split view drops its fixed toolbar. The old toolbar mirrored the split flex geometry above the panes with scrollLeft syncing. Each pane now renders an in-flow header (static title + split/close actions), which deletes the geometry mirroring, the scroll sync, and three viewport-specific CSS inset hacks.
• Session workspace rail docks right or bottom. Drag the rail header onto the pane's right/bottom band (drop zones highlight, mirroring the terminal panel) or use the dock toggle button. The preference persists browser-locally (chatWorkspaceDock, only written when non-default). The collapsed strip's file glyph is now a real "Show session files" button with a changed-file count badge.
• Mac app compatibility. The native drag-region geometry (78-254px brand strip) is unchanged; the web topbar keeps that strip passive/non-interactive on openclaw-native-macos so shipped Mac apps keep working against a new gateway UI. The injected chrome CSS drops its two desktop padding rules (now web-owned); the settings-sidebar header class rename and the panel's non-sidebar-shell container keep stale injected padding from double-applying during app/gateway version drift, and the narrow-width drawer gets web-owned titlebar clearance.

User Impact

• Full-width content on every page with a slim 48px topbar; the session panel reads as content, not chrome, and can be hidden entirely (Cmd+B).
• Split view panes get honest per-pane title bars; the topbar stays put instead of appearing only in split view.
• The session workspace rail can live on the right or the bottom of its pane, per user preference, moved by drag or button; the dead collapsed-strip icon now works and shows the changed-file count.
• Narrow viewports keep the existing drawer flow (drawer holds brand + nav + sessions + utility footer).
• Docs: https://docs.openclaw.ai/web/control-ui

Screenshots (mock gateway, deterministic):

Overview	Chat split	More menu

Panel hidden	Rail right dock	Rail bottom dock

Settings takeover	Drawer (900px)	Dark split

Evidence

• Remote (Blacksmith Testbox): full pnpm check:changed green, exit 0 (lint/type/guard lanes + 5 Vitest shards), actions run 29070305914.
• Remote focused units: pnpm test over chat-page, chat-view, chat-session-workspace, app-sidebar, settings.node, app-navigation, app-host — 241 passed. chat-realtime.test.ts fails on the box even when run alone with an untouched import graph (localStorage.clear is not a function in its own beforeEach); documented pre-existing environment quirk, green on CI Linux.
• Local e2e (Playwright Chromium, mock gateway): chat-flow.e2e.test.ts 37/37, sidebar-customization.e2e.test.ts 2/2, mobile-pairing.e2e.test.ts 1/1 — all three rewritten/touched by this PR.
• pnpm ui:i18n:sync + pnpm ui:i18n:check clean (keyless raw-copy fallbacks, matching CI).
• Visual proof: ten deterministic mock-gateway screenshots above (light + dark, desktop + drawer + both docks).
• swiftformat (repo config): changed Swift regions clean; two pre-existing wrap findings elsewhere in DashboardWindowSmokeTests.swift are local-version drift, untouched.
• Autoreview (Codex gpt-5.5, thinking high): feature commit reviewed with one accepted P2 (native macOS drawer lost its titlebar clearance at narrow widths), fixed in the follow-up commit; the fix commit re-reviewed clean ("no accepted/actionable findings").