Rules and chrome scale with the display's density; dark pages get visible separators and focus tints

Density: dp() in gui.zig draws every size given in pixels in logical
pixels (SDL's window display scale, rounded, at least one), as acme scales
Border, ButtonBorder and Scrollgap: the rules (rule_px), the tag rule, the
grip's ring, its dirty gap and mode bars, the rail's gap to the text and
its minimum, the thumb's inset, the rim, a bar cursor's minimum width,
underline and strikethrough thickness (the atlas is dropped on a scale
change), the rule-grab margin, and the Crt's scanline and mask periods
(pardesScale in the post prefix). Cell- and tagline-measured sizes stay:
the rail's width, Lift's blur and offsets, every motion; iResolution,
fragCoord and iMouse stay in the display's pixels, as ghostty's.
PARDES_TEST_SCALE forces a density in a harness (a test window is 1x
otherwise, whatever display it lands on) and sizes the test font with it.

Colours: a separator that stands off its page by less than 1.5:1 is lifted
toward the text to 1.6:1 (helix, atelier, paper; a theme with no page,
dark, is judged against #121212), and empty_col follows it. forge's own
rule already stands at 3.83:1; what hid it was density: 2 device pixels
on a 3x screen, now 6 (dp). A focused tag's tint closer than 1.5:1 to the
plain tag on a dark page (1.25:1 on a light one) is pushed further the way
it leans, as far as its text keeps its own contrast or 4.5: forge
1.23 -> 1.51 (#2d3440 -> #374253), and likewise dusk, orchard, ink,
lagoon, clay, harvest, spectrum, solarium, forge_soft; daybreak, atelier,
paper to 1.25. dark and helix gain a tint of their own (dark: #484566
under #c8c8c8, 1.54:1; helix: ramp 237 under 250, 1.65:1).

Tag caret: past a full row's end, the G3 glide box sits on the tag's right
edge, where the layer's caret and the pixel shell's are.

Tests: every native theme's separator >= 1.5 and every dark one has a
tint >= 1.25 with readable text; forge keeps its own border; the tag caret
glide box at a full row; at 2x the spine, tag rule, ring, rail start and
gap, and bar cursor double. Legacy-ThemeFile test strips helix's new pair.

Goldens: snapshot goldens change in colour rows only, the tints (orchard
#283a2f -> #314738 at boot, forge, helix and dark in theme/themesel).
GUI goldens: the harness's single Del of the renamed wide pane is refused
since ysqnkyoy (a rename counted as unsaved; fixed on the 9P line in
wkzlsqvy), so scenes 09-17 were recorded with that pane open and the file
was stale since the merge (08 and 18 also moved with ykvnltvs's full-row
tag wrap). The goldens here were recorded with that pane closed (as
wkzlsqvy will close it); against the parent's binary under the same
conditions they differ only in the tints: 01-13 forge's (#2d3440 ->
#374253, and the glyph edges on it), 14 ink's; 15-18 are byte-identical.
Until wkzlsqvy is merged, a run here fails 09-17. Each commit reproduces its own
recorded goldens on this machine (checked at kvtmqkyn). A test window is
1x unless PARDES_TEST_SCALE says otherwise, whatever display it opens on.
Prebuilt shaders refreshed from their sources.
Captures: .scratch/render/dark-borders/{before,after,compare,scale2,scale3}.

2 files changed, 8 insertions, 0 deletions

diff --git a/src/themes/dark.zig b/src/themes/dark.zig
index 82396397..e93fd489 100644
--- a/src/themes/dark.zig
+++ b/src/themes/dark.zig
@@ -17,6 +17,10 @@ pub const theme = .{
     .sel_fg = .{ 0xd8, 0xc8, 0xa8 },
     .tag_bg = .{ 0x2c, 0x2a, 0x3e },
     .tag_fg = .{ 0x96, 0x96, 0x96 },
+    // The focused tag: its band lighter in its own hue (1.54:1 off the
+    // plain one), its ink lighter to keep reading on it.
+    .tag_active_bg = .{ 0x48, 0x45, 0x66 },
+    .tag_active_fg = .{ 0xc8, 0xc8, 0xc8 },
     .box = .{ 0x66, 0x3f, 0xe0 },
     .box_dim = .{ 0x35, 0x3a, 0x58 },
     .kw = .{ 0xda, 0x5e, 0xea },
diff --git a/src/themes/helix.zig b/src/themes/helix.zig
index db51de3a..61dc8e63 100644
--- a/src/themes/helix.zig
+++ b/src/themes/helix.zig
@@ -43,6 +43,10 @@ pub const theme = .{
     .sel_fg = .{ 0x08, 0x08, 0x08 },
     .tag_bg = .{ 0x12, 0x12, 0x12 },
     .tag_fg = .{ 0x94, 0x94, 0x94 },
+    // The focused tag, still on the ramp: 237 #3a3a3a under 250 #bdbdbd
+    // (the page's text), 1.65:1 off the plain bar.
+    .tag_active_bg = .{ 0x3a, 0x3a, 0x3a },
+    .tag_active_fg = .{ 0xbd, 0xbd, 0xbd },
     .box = .{ 0x62, 0x62, 0x62 },
     .box_dim = .{ 0x26, 0x26, 0x26 },
     .kw = .{ 0xd7, 0x76, 0xf9 },