Initial scaffold: spec, architecture playbook, and M0 skeleton

styles/base.css

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+@import './tokens.css';
+
+* {
+  box-sizing: border-box;
+}
+
+html,
+body,
+#app {
+  height: 100%;
+  margin: 0;
+}
+
+body {
+  font-family: var(--font-sans);
+  font-size: var(--font-size-base);
+  color: var(--color-text);
+  background: var(--color-bg);
+}
+
+@media (prefers-reduced-motion: reduce) {
+  *,
+  *::before,
+  *::after {
+    animation-duration: 0.01ms !important;
+    transition-duration: 0.01ms !important;
+  }
+}

styles/tokens.css

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+/*
+ * Design tokens. Borrowed in spirit from Syto: a single source of truth for
+ * colors/spacing/typography, themable by overriding the custom properties on
+ * a [data-theme] root. Concrete values are placeholders pending the design pass.
+ */
+:root {
+  /* Palette */
+  --color-bg: #ffffff;
+  --color-surface: #f7f7fa;
+  --color-border: #e2e2ea;
+  --color-text: #1a1a2e;
+  --color-text-muted: #6b6b80;
+  --color-accent: #3b5bdb;
+  --color-accent-contrast: #ffffff;
+
+  /* Status */
+  --color-success: #2f9e44;
+  --color-error: #e03131;
+  --color-warning: #f08c00;
+  --color-info: #1971c2;
+
+  /* Typography */
+  --font-sans: system-ui, -apple-system, 'Segoe UI', Roboto, sans-serif;
+  --font-mono: ui-monospace, 'SF Mono', 'Cascadia Code', Menlo, monospace;
+  --font-size-base: 14px;
+
+  /* Spacing scale */
+  --space-1: 4px;
+  --space-2: 8px;
+  --space-3: 12px;
+  --space-4: 16px;
+  --space-6: 24px;
+
+  /* Layout */
+  --header-height: 48px;
+  --radius: 6px;
+}
+
+[data-theme='experimental'] {
+  --color-bg: #16161f;
+  --color-surface: #1f1f2c;
+  --color-border: #2c2c3a;
+  --color-text: #e8e8f0;
+  --color-text-muted: #9a9ab0;
+  --color-accent: #748ffc;
+  --color-accent-contrast: #0b0b12;
+}