feat(app): CSS-variable theming with dark/light palettes and accents

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/src/theme.ts

@@ -2,23 +2,23 @@ import type { SurfaceState } from "./layoutTypes";
 
 /** Design tokens — mirror of DOCS/space-sh.pen variables. Single source for the UI. */
 export const COLORS = {
-  accent: "#4C8DFF",
-  bgApp: "#0E1116",
-  bgElevated: "#1A2029",
-  bgHover: "#222A35",
-  bgPanel: "#0A0D12",
-  bgSidebar: "#13171F",
-  borderStrong: "#323C49",
-  borderSubtle: "#232A33",
-  textPrimary: "#E6EDF3",
-  textSecondary: "#8B97A6",
-  textMuted: "#5A6573",
-  stWork: "#4C8DFF",
-  stWait: "#F2B84B",
-  stDone: "#3FB950",
-  stError: "#F4544E",
-  stIdle: "#5A6573",
-  searchMatch: "#5A4A1F",
+  accent:        "var(--c-accent)",
+  bgApp:         "var(--c-bg-app)",
+  bgElevated:    "var(--c-bg-elevated)",
+  bgHover:       "var(--c-bg-hover)",
+  bgPanel:       "var(--c-bg-panel)",
+  bgSidebar:     "var(--c-bg-sidebar)",
+  borderStrong:  "var(--c-border-strong)",
+  borderSubtle:  "var(--c-border-subtle)",
+  textPrimary:   "var(--c-text-primary)",
+  textSecondary: "var(--c-text-secondary)",
+  textMuted:     "var(--c-text-muted)",
+  stWork:        "var(--c-st-work)",
+  stWait:        "var(--c-st-wait)",
+  stDone:        "var(--c-st-done)",
+  stError:       "var(--c-st-error)",
+  stIdle:        "var(--c-st-idle)",
+  searchMatch:   "var(--c-search-match)",
 } as const;
 
 export const FONT = {
@@ -35,3 +35,72 @@ export const STATE_COLOR: Record<SurfaceState | "stopped", string> = {
   idle:    COLORS.stIdle,
   stopped: COLORS.stIdle,
 };
+
+// ---------------------------------------------------------------------------
+// Palettes
+// ---------------------------------------------------------------------------
+
+type Palette = Record<string, string>;
+
+/** Dark palette — hex values identical to what COLORS contained before. */
+const DARK: Palette = {
+  "bg-app":         "#0E1116",
+  "bg-elevated":    "#1A2029",
+  "bg-hover":       "#222A35",
+  "bg-panel":       "#0A0D12",
+  "bg-sidebar":     "#13171F",
+  "border-strong":  "#323C49",
+  "border-subtle":  "#232A33",
+  "text-primary":   "#E6EDF3",
+  "text-secondary": "#8B97A6",
+  "text-muted":     "#5A6573",
+  "st-work":        "#4C8DFF",
+  "st-wait":        "#F2B84B",
+  "st-done":        "#3FB950",
+  "st-error":       "#F4544E",
+  "st-idle":        "#5A6573",
+  "search-match":   "#5A4A1F",
+};
+
+/** Light palette — a readable counterpart for every token. */
+const LIGHT: Palette = {
+  "bg-app":         "#F5F7FA",
+  "bg-elevated":    "#FFFFFF",
+  "bg-hover":       "#E8EDF3",
+  "bg-panel":       "#EBEEF3",
+  "bg-sidebar":     "#DDE3EC",
+  "border-strong":  "#B0BAC7",
+  "border-subtle":  "#CDD4DE",
+  "text-primary":   "#0D1117",
+  "text-secondary": "#4A5568",
+  "text-muted":     "#8898AA",
+  "st-work":        "#2266CC",
+  "st-wait":        "#C07800",
+  "st-done":        "#1A7A30",
+  "st-error":       "#C4231F",
+  "st-idle":        "#8898AA",
+  "search-match":   "#FDE68A",
+};
+
+export const ACCENTS: Record<string, string> = {
+  blue:   "#4C8DFF",
+  teal:   "#34D3C2",
+  purple: "#9B7BFF",
+  green:  "#3FB950",
+  orange: "#F2934B",
+};
+
+export type ThemeName = "dark" | "light";
+
+/** Real color values for consumers that can't use var() (xterm). Keys are the kebab tokens plus "accent". */
+export function resolvePalette(theme: ThemeName, accent: string): Record<string, string> {
+  const base = theme === "light" ? LIGHT : DARK;
+  return { ...base, accent: ACCENTS[accent] ?? ACCENTS.blue };
+}
+
+/** Write the active palette to :root as --c-* custom properties. */
+export function applyTheme(theme: ThemeName, accent: string): void {
+  const p = resolvePalette(theme, accent);
+  const root = document.documentElement.style;
+  for (const [k, v] of Object.entries(p)) root.setProperty(`--c-${k}`, v);
+}