Feature request: Move sidebar toggle and note tabs into the title bar

[junereycasuga]

I'd like to reclaim the centered title area in the title bar and use it for more useful controls.

Current behavior

• The title bar shows a centered window title.
• The sidebar hide/show toggle lives inside the sidebar header.
• Note tabs live inside each editor pane, below the title bar.
• This uses vertical space and leaves the title bar mostly decorative.

Desired behavior

• Remove/hide the centered title from the title bar.
• Move the sidebar hide/show toggle into the title bar.
• Move the note tab strip into the title bar.
• Ideally this would be doable with CSS overrides, but since tabs and toggles are separate React components it may need a small structural change.

Mock layout

  +--------------------------------------------------+
  | [≡] [tab-1] [tab-2] [tab-3*]         [—] [□] [×] |
  +--------------------------------------------------+
  | sidebar | editor / preview content                 |

Why

• Saves vertical space.
• Keeps navigation controls in a predictable top bar, similar to VS Code, browsers, and other tabbed apps.
• The current centered title is redundant with the active note name already shown in the tab/breadcrumb.

Scope / edge cases

• Should work for single-pane layouts.
• When split into multiple panes, the title bar could either stay empty or fall back to the centered title while each pane keeps its inline tabs.
• On macOS the traffic-light area must stay reserved.
• On Windows/Linux the window controls must remain reachable.