fix(tui): reassign Dune to dark Claude Code colorblind palette

docs/THEMES.md

@@ -11,8 +11,9 @@ the active theme and the registered names without opening the picker.
 
 ## Dune (`dune`)
 
-A warm sand-and-cream palette: sand/cream surface, charcoal ink, and a soft
-amber accent.
+A dark, colorblind-safe palette matching Claude Code's daltonized dark mode:
+near-black surface, white ink, and a deuteranopia-adjusted brand-orange
+accent.
 
 ## Neon (`neon`)
 

internal/tui/theme_palettes.go

@@ -433,36 +433,41 @@ var solarizedLightPalette = palette{
 	cardPerm:  "#c4ae63",
 }
 
-// dunePalette is a warm sand-and-cream color scheme: sand/cream surface,
-// charcoal ink, and a soft amber accent.
+// dunePalette is a dark theme based on Claude Code's colorblind-friendly
+// (daltonized) dark mode. The base surface is near-black (Claude Code's true
+// dark canvas), with white ink and the brand-orange accent adjusted for
+// deuteranopia. Diff signals reuse the proven dark-theme structure so every
+// WCAG-AA invariant still holds; the accent and status colors (blue success,
+// red error, amber warning) follow Claude Code's daltonized palette so
+// additions stay distinguishable under color blindness.
 var dunePalette = palette{
-	panel:     "#f2e9d8",
-	promptBg:  "#e9dcbf",
-	line:      "#d9c7a3",
-	line2:     "#c2a97c",
-	ink:       "#2b241a",
-	muted:     "#473e32",
-	faint:     "#554a3a",
-	faintest:  "#655648",
-	accent:    "#724028", // darkened from #8f5215 for AA on selBg (5.46:1) that also survives ANSI-256 downsampling (quantizes to #444444, 6.47:1 on quantized selBg; the previous #7c4712 quantized to #875f00 at 3.81:1)
-	green:     "#38572a",
-	red:       "#872d24", // darkened from #963328 so delBg contrast survives ANSI-256 downsampling (true 6.57:1, 256 7.86:1)
-	amber:     "#6d4600",
-	blue:      "#2f5680", // darkened from #3d6a9e for AA on selBg (was 3.61:1, now 4.90:1)
-	gitAdd:    "#38572a",
-	gitDel:    "#963328",
-	addBg:     "#dcecd0",
-	delBg:     "#f5dbd5",
-	addBgWord: "#b9dc9e",
-	delBgWord: "#eebba9",
-	permBg:    "#f0dfae",
-	selBg:     "#e0cf98",
-	addInk:    "#264018",
-	delInk:    "#5c1810",
-	onAccent:  "#fdf6ea",
-	cardRun:   "#b08a4a",
-	cardErr:   "#b57560",
-	cardPerm:  "#c2a04a",
+	panel:     "#0e0e10", // Claude Code dark canvas — near-black
+	promptBg:  "#262626", // submitted user-prompt bubble
+	line:      "#242429", // borders/separators
+	line2:     "#414147",
+	ink:       "#ececee",
+	muted:     "#ccccd2", // secondary text — bright gray, top of the ramp
+	faint:     "#b8b8c0", // hints/metadata
+	faintest:  "#55c6cd", // line numbers/separators — a neutral gray at this brightness quantizes to xterm #005f00's near-neighbor at only 2.97:1 on the add-diff gutter; nudging toward cyan (still under the faint/faintest/panel ramp) keeps AA (4.62:1) once xterm-256 rounds it
+	accent:    "#ff9628", // brand/claude rgb(255,150,40), adjusted for deuteranopia
+	green:     "#5eccfa", // success — brightened past Claude Code's rgb(51,153,255) so the add-diff sign text stays AA (4.80:1) against addBg once xterm-256 quantizes both to #5fd7ff/#005f00 (2.43:1 at the original value)
+	red:       "#ff6666", // error rgb(255,102,102)
+	amber:     "#ffcc00", // warning rgb(255,204,0)
+	blue:      "#99ccff", // permission rgb(153,204,255)
+	gitAdd:    "#7db87a",
+	gitDel:    "#b87a7a",
+	addBg:     "#003500", // diff added band — quantizes to xterm green #005f00 instead of the same gray as delBg, keeping add/del rows distinct on 256-color terminals (previous #0a1f14/#240a0e both collapsed to #121212)
+	delBg:     "#350000", // diff removed band — quantizes to xterm red #5f0000 (see addBg)
+	addBgWord: "#007400", // word-level added span — quantizes to xterm green #008700, distinct from both addBg's #005f00 and delBgWord's red
+	delBgWord: "#740000", // word-level removed span — quantizes to xterm red #870000 (see addBgWord)
+	permBg:    "#1c1915",
+	selBg:     "#262626", // selection — dark gray, distinct from panel (>= 1.10 contrast after xterm-256 quantization), AA with faint/faintest
+	addInk:    "#f0f5d2", // changed-word text — lightened so it still clears AA (4.60:1) against addBgWord's xterm-256 quantized #008700 (the original #bdeed7 fell to 4.06:1)
+	delInk:    "#f2c4c4",
+	onAccent:  "#000000",
+	cardRun:   "#3399ff", // success blue
+	cardErr:   "#ff6666", // error
+	cardPerm:  "#ffcc00", // warning
 }
 
 // themeEntry is one registered theme: Name is the /theme value + ZERO_THEME/--theme
@@ -491,9 +496,9 @@ var themeRegistry = []themeEntry{
 	{Name: "rose-pine", Label: "Rosé Pine", Palette: rosePinePalette, IsDark: true},
 	{Name: "everforest", Label: "Everforest", Palette: everforestPalette, IsDark: true},
 	{Name: "neon", Label: "Neon", Palette: neonPalette, IsDark: true},
+	{Name: "dune", Label: "Dune", Palette: dunePalette, IsDark: true},
 	{Name: "light", Label: "light", Palette: lightPalette, IsDark: false},
 	{Name: "solarized-light", Label: "Solarized Light", Palette: solarizedLightPalette, IsDark: false},
-	{Name: "dune", Label: "Dune", Palette: dunePalette, IsDark: false},
 }
 
 // themeByName indexes the registry by lowercased name for O(1) lookup. Built as a

internal/tui/theme_select_test.go

@@ -275,8 +275,8 @@ func TestNewThemePresetsWired(t *testing.T) {
 	if !ok {
 		t.Fatal("theme 'dune' is not registered")
 	}
-	if dune.IsDark {
-		t.Error("theme 'dune' should be marked as light")
+	if !dune.IsDark {
+		t.Error("theme 'dune' should be marked as dark")
 	}
 
 	for _, name := range []string{"neon", "dune"} {
@@ -408,15 +408,30 @@ func xterm256Hex(t *testing.T, hexColor string) string {
 // terminal, which quantizes every token to its nearest xterm entry first.
 // Guard the pairs that regressed: Dune's selected-row affordances (accent
 // caret/favorite star and blue local-model dot over selBg via onSel) and
-// Neon's diff bands, whose previous values all quantized to the same grays.
+// diff bands (whose previous addBg/delBg and addBgWord/delBgWord values all
+// quantized to the same grays), plus the rendered add-diff content itself
+// (gutter and changed-word text, which quantization made unreadable even
+// once the bands were distinct), and Neon's diff bands with the same issues.
 func TestExtendedThemeANSI256Contrast(t *testing.T) {
 	palettes := map[string]palette{}
 	for _, entry := range themeRegistry {
 		palettes[entry.Name] = entry.Palette
 	}
 	q := func(hexColor string) string { return xterm256Hex(t, hexColor) }
 
+	greenish := func(hexColor string) bool {
+		r, g, b := hexChannels(t, hexColor)
+		return g > r && g > b
+	}
+	reddish := func(hexColor string) bool {
+		r, g, b := hexChannels(t, hexColor)
+		return r > g && r > b
+	}
+
 	dune := palettes["dune"]
+	if sep := wcagRatio(t, q(dune.selBg), q(dune.panel)); sep < 1.10 {
+		t.Errorf("dune: selBg vs panel separation %.2f < 1.10 after xterm-256 quantization (%s vs %s)", sep, q(dune.selBg), q(dune.panel))
+	}
 	for _, pair := range []struct{ name, fg, bg string }{
 		{"accent on selBg", dune.accent, dune.selBg},
 		{"blue on selBg", dune.blue, dune.selBg},
@@ -427,16 +442,45 @@ func TestExtendedThemeANSI256Contrast(t *testing.T) {
 			t.Errorf("dune: %s = %.2f < 4.5 after xterm-256 quantization (%s on %s)", pair.name, r, q(pair.fg), q(pair.bg))
 		}
 	}
-
-	neon := palettes["neon"]
-	greenish := func(hexColor string) bool {
-		r, g, b := hexChannels(t, hexColor)
-		return g > r && g > b
+	// Dune's diff row/word bands must keep the same add/del distinctness on
+	// 256-color terminals that Neon's already guard below: the original
+	// addBg/delBg (#0a1f14/#240a0e) both quantized to the same gray (#121212),
+	// making added and removed lines indistinguishable.
+	if q(dune.addBg) == q(dune.delBg) || !greenish(q(dune.addBg)) || !reddish(q(dune.delBg)) {
+		t.Errorf("dune: add/del row bands lose their green/red identity after quantization: addBg %s -> %s, delBg %s -> %s",
+			dune.addBg, q(dune.addBg), dune.delBg, q(dune.delBg))
 	}
-	reddish := func(hexColor string) bool {
-		r, g, b := hexChannels(t, hexColor)
-		return r > g && r > b
+	if q(dune.addBgWord) == q(dune.delBgWord) || !greenish(q(dune.addBgWord)) || !reddish(q(dune.delBgWord)) {
+		t.Errorf("dune: word-span bands lose their green/red identity after quantization: addBgWord %s -> %s, delBgWord %s -> %s",
+			dune.addBgWord, q(dune.addBgWord), dune.delBgWord, q(dune.delBgWord))
+	}
+	if q(dune.addBgWord) == q(dune.addBg) {
+		t.Errorf("dune: changed span is indistinguishable from its add row after quantization (both %s)", q(dune.addBg))
+	}
+	if q(dune.delBgWord) == q(dune.delBg) {
+		t.Errorf("dune: changed span is indistinguishable from its del row after quantization (both %s)", q(dune.delBg))
+	}
+	if r := wcagRatio(t, q(dune.green), q(dune.addBg)); r < 4.5 {
+		t.Errorf("dune: green on addBg = %.2f < 4.5 after quantization", r)
+	}
+	if r := wcagRatio(t, q(dune.red), q(dune.delBg)); r < 4.5 {
+		t.Errorf("dune: red on delBg = %.2f < 4.5 after quantization", r)
 	}
+	// The two rendered diff-content pairs a 256-color terminal actually shows:
+	// line numbers (faintest on addBg/delBg) and highlighted changed spans
+	// (addInk/delInk on their word bands). Mirrors the Neon assertions below.
+	for _, pair := range []struct{ name, fg, bg string }{
+		{"faintest on addBg", dune.faintest, dune.addBg},
+		{"faintest on delBg", dune.faintest, dune.delBg},
+		{"addInk on addBgWord", dune.addInk, dune.addBgWord},
+		{"delInk on delBgWord", dune.delInk, dune.delBgWord},
+	} {
+		if r := wcagRatio(t, q(pair.fg), q(pair.bg)); r < 4.5 {
+			t.Errorf("dune: %s = %.2f < 4.5 after quantization (%s on %s)", pair.name, r, q(pair.fg), q(pair.bg))
+		}
+	}
+
+	neon := palettes["neon"]
 	if q(neon.addBg) == q(neon.delBg) || !greenish(q(neon.addBg)) || !reddish(q(neon.delBg)) {
 		t.Errorf("neon: add/del row bands lose their green/red identity after quantization: addBg %s -> %s, delBg %s -> %s",
 			neon.addBg, q(neon.addBg), neon.delBg, q(neon.delBg))