Initialize repository with harness code and assets

Initial import of all source code, config, and README assets: the
packages workspace (cli, core, server, web, docs, landing, skills),
build scripts, tooling config, and CI workflows.

Includes the data-layout revision made on this branch: the local data
root defaults to ~/.penguin/data (PENGUIN_HOME still overrides; the
installer keeps its binaries in ~/.penguin), and every Agent lives
under <project>/agents/<agent>/ — path helpers, the three
agent-enumeration scans, the system prompt, built-in Skills, tests
and docs all follow the new layout.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018ihk8iQuo3kv2aPjAYEPuR

packages/docs/src/state/theme.tsx

@@ -0,0 +1,64 @@
+/**
+ * Theme context: light / dark / system (tracks prefers-color-scheme live), toggled
+ * via the html.dark class + Tailwind dark: variant, persisted to localStorage.
+ * Same behavior as the landing page, under the docs site's own storage key
+ * (index.html pre-applies the stored value before first paint).
+ */
+import { createContext, useCallback, useContext, useEffect, useState } from "react";
+import type { ReactNode } from "react";
+
+export type ThemeMode = "light" | "dark" | "system";
+
+const MODE_KEY = "penguin-docs.theme";
+
+interface ThemeContextValue {
+  mode: ThemeMode;
+  /** Resolved effective theme (system mode resolved against the OS preference). */
+  dark: boolean;
+  setMode: (mode: ThemeMode) => void;
+}
+
+const ThemeContext = createContext<ThemeContextValue | null>(null);
+
+function initialMode(): ThemeMode {
+  const stored = localStorage.getItem(MODE_KEY);
+  if (stored === "light" || stored === "dark" || stored === "system") return stored;
+  return "system";
+}
+
+function systemDark(): boolean {
+  return window.matchMedia("(prefers-color-scheme: dark)").matches;
+}
+
+export function ThemeProvider({ children }: { children: ReactNode }) {
+  const [mode, setModeState] = useState<ThemeMode>(initialMode);
+  const [sysDark, setSysDark] = useState(systemDark);
+
+  const dark = mode === "system" ? sysDark : mode === "dark";
+
+  useEffect(() => {
+    document.documentElement.classList.toggle("dark", dark);
+  }, [dark]);
+
+  useEffect(() => {
+    if (mode !== "system") return;
+    const mq = window.matchMedia("(prefers-color-scheme: dark)");
+    const onChange = (e: MediaQueryListEvent) => setSysDark(e.matches);
+    setSysDark(mq.matches);
+    mq.addEventListener("change", onChange);
+    return () => mq.removeEventListener("change", onChange);
+  }, [mode]);
+
+  const setMode = useCallback((next: ThemeMode) => {
+    localStorage.setItem(MODE_KEY, next);
+    setModeState(next);
+  }, []);
+
+  return <ThemeContext.Provider value={{ mode, dark, setMode }}>{children}</ThemeContext.Provider>;
+}
+
+export function useTheme(): ThemeContextValue {
+  const ctx = useContext(ThemeContext);
+  if (!ctx) throw new Error("useTheme must be used inside ThemeProvider");
+  return ctx;
+}