* Add "Match Terminal Background" sidebar setting
Adds a toggle in Settings > Sidebar Appearance that makes the sidebar
use the same background color and transparency as the terminal area.
Uses layer-level opacity on a fully opaque background color (the same
technique as TitlebarLayerBackground) with effective opacity formula
`1 - (1-alpha)^2` to account for the terminal's two stacked
semi-transparent layers (Bonsplit chrome + Ghostty Metal surface).
Also adds a 1px trailing border derived from the terminal chrome color,
matching the bonsplit tab bar separator logic.
* Fix sidebar border color not updating on theme change
Add @State + .onReceive(.ghosttyDefaultBackgroundDidChange) to
SidebarTrailingBorder so the separator color recomputes when the
Ghostty theme changes, matching the pattern used in SidebarBackdrop.
* Address review comments: localize debug toggle, fix separator refresh
- Localize the debug panel toggle label (Codex P1)
- Add .onAppear to SidebarTrailingBorder for initial color (Cubic P2)
- Fix stale doc comment on SidebarTerminalBackgroundView (Cubic P3)
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Co-authored-by: Lawrence Chen <lawrencecchen@users.noreply.github.com>
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