fix(render): DPI-scale terminal padding and border offsets

[forketyfork]

Summary

A recent PR increased border thickness and made it DPI-aware. Two layout bugs followed in grid view on Retina displays.

The CWD bar (current directory display) was overlapping the bottom border. reservedHeight() and renderCwdBar() both read the raw grid_border_thickness constant (6 logical px) without scaling it, so on 2x displays the bar ended up positioned too high by the scaling difference.

The border was also drawing over terminal content. terminal_padding = 8 is a logical pixel value but was used as raw physical pixels throughout renderSessionContent, terminalContentRect, and the session interaction hit-testing path. On 2x Retina the DPI-scaled border is 12px, which exceeds the 8px padding, so the border ate into the content area.

Both are fixed by applying dpi.scale() where the raw constants were used. For terminal padding, ui_scale is now threaded through to renderSessionContent and terminalContentRect in both renderer.zig and session_interaction.zig.

Test plan

• In grid view on a Retina (2x DPI) display, verify the CWD bar sits flush inside the border with no overlap at the bottom edge
• Verify terminal text is not obscured by the border on any edge
• Check on a 1x display to confirm no regression (padding should remain visually equivalent)

[Copilot]

Pull request overview

Fixes DPI-scaling issues in grid view rendering by ensuring border thickness and terminal padding are treated as logical units and scaled to physical pixels via dpi.scale().

Changes:

• DPI-scale grid_border_thickness usage in CWD bar layout so it no longer overlaps the bottom border on Retina displays.
• DPI-scale terminal_padding in terminal content rendering and terminal content rect calculation.
• Thread ui_scale into renderSessionContent / terminalContentRect call paths (renderer + session interaction scrollbar context).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
src/ui/components/session_interaction.zig	Scales terminal content rect padding for scrollbar layout (now takes ui_scale).
src/ui/components/cwd_bar.zig	Scales grid border thickness when reserving height and positioning the CWD bar.
src/render/renderer.zig	Scales terminal padding during content rendering and content-rect computation; threads ui_scale into rendering.

Comments suppressed due to low confidence (1)

src/render/renderer.zig:377

• renderSessionContent now uses DPI-scaled terminal_padding, but term_cols/term_rows appear to be computed elsewhere using the unscaled constant. On high-DPI displays this will make term_cols/term_rows larger than what fits in drawable_w/drawable_h, causing the right/bottom of the terminal to be clipped (since visible_cols/rows are capped by max_*_fit). Consider updating the terminal sizing / PTY pixel size calculations to use dpi.scale(terminal_padding, ui_scale) (or threading ui_scale into those helpers) so sizing and rendering stay consistent.

    const padding: c_int = dpi.scale(terminal_padding, ui_scale);
    const drawable_w: c_int = rect.w - padding * 2;
    const drawable_h: c_int = rect.h - padding * 2;
    if (drawable_w <= 0 or drawable_h <= 0) return;

    const origin_x: c_int = rect.x + padding;
    const origin_y: c_int = rect.y + padding;

    const max_cols_fit: usize = @intCast(@max(0, @divFloor(drawable_w, cell_width_actual)));
    const max_rows_fit: usize = @intCast(@max(0, @divFloor(drawable_h, cell_height_actual)));
    const visible_cols: usize = @min(@as(usize, term_cols), max_cols_fit);
    const visible_rows: usize = @min(@as(usize, term_rows), max_rows_fit);

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