Merge christianhaberl's session-sidebar branch, ported to current master

Brings in https://github.com/christianhaberl/Codeman/pull/4 (three commits,
authorship preserved) and adapts it across the 211 commits master gained
since the branch was cut:

- App Settings control re-authored for the set-* surface (PR #278): a
  set-row in Layout -> Tabs, replacing the old settings-item markup the
  branch targeted. i18n description synced.
- Lineage arcs (PR #291, post-branch) are SKIPPED in sidebar layout:
  computeLineagePath()'s U-bridge geometry hangs from the horizontal
  strip's bottom edge and has no meaning against a vertical list. The
  lineage strip-scroll listener now also redraws subagent/ultracode
  connectors while the sidebar scrolls vertically.
- The desktop home tab rail (post-branch) defers to the sidebar: both dock
  the session list flush left, and the rail would render z-ordered under it.
- Active-row reveal unified into _scrollActiveTabIntoView() (#257 landed on
  master after the branch): sidebar mode branches to scrollIntoView
  block:'nearest', and _fullRenderSessionTabs() restores scrollTop alongside
  the #257 scrollLeft restore so ambient rebuilds cannot yank a mid-scroll
  sidebar back to the top.
- Mobile active-tab hoisting the branch guarded against no longer exists on
  master (removed by #257); kept master's order-stable render.

Verified: typecheck, lint, format:check, check:frontend-syntax,
check:public-assets, PostCSS parse of both merged stylesheets, the 26 new
jsdom tests, the structural guard suites, and the headless-Chromium harness
(scripts/verify-session-sidebar.mts) green across all seven layout states
at 1600/1000/393px against current master.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/web/public/terminal-ui.js

@@ -326,6 +326,17 @@ Object.assign(CodemanApp.prototype, {
         return true;
       }
 
+      // Session-sidebar toggle chord (default Alt+B): same trap as above —
+      // preventDefault() in the capture handler does not stop xterm, so without
+      // this gate every toggle would ALSO send ESC b (readline backward-word)
+      // into the live session and walk the cursor back through the user's
+      // half-typed prompt. Registry-aware and only while the sidebar layout is
+      // active, so a rebind/disable and the default header layout keep plain
+      // Meta-b working in the terminal.
+      if (ev.type === 'keydown' && this.shouldToggleSessionSidebarFromShortcut?.(ev)) {
+        return false;
+      }
+
       // Ctrl+V / Cmd+V: intercept before xterm sends ^V to PTY.
       // Route through our paste trap which handles both images and text.
       if ((ev.ctrlKey || ev.metaKey) && ev.key === 'v' && ev.type === 'keydown') {