Add desktop tray widget + installer wizard

- Desktop widget (Python/pystray): system tray icon showing 5h usage as
  circular progress bar with Claude starburst logo, 10-step green-to-red
  color scale, right-click menu with usage stats and configuration
- Shared cache: both widget and CLI statusline read/write the same
  /tmp/claude_usage.json — only one fetcher needs to run
- Installer wizard (install_wizard.py): interactive cross-platform setup
  with component selection, session key prompt, cron/autostart config
- OS wrappers: install.sh (Linux/macOS) and install.ps1 (Windows) find
  Python 3.9+ and launch the wizard
- README with topology diagram, usage docs, and configuration reference

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

claude_usage_widget/app.py

@@ -0,0 +1,91 @@
+"""Main orchestrator: tray icon, state, threads."""
+
+import logging
+import sys
+import threading
+import tkinter as tk
+from tkinter import simpledialog
+
+import pystray
+
+from . import config
+from .fetcher import UsageFetcher
+from .menu import build_menu
+from .renderer import render_icon
+
+log = logging.getLogger(__name__)
+
+
+class App:
+    def __init__(self):
+        self.usage_data = {}
+        self._lock = threading.Lock()
+        self.fetcher = UsageFetcher(on_update=self._on_usage_update)
+        self._icon = pystray.Icon(
+            name="claude-usage",
+            icon=render_icon(0),
+            title="Claude Usage Widget",
+            menu=build_menu(self),
+        )
+
+    def run(self):
+        """Start fetcher and run tray icon (blocks until quit)."""
+        self.fetcher.start()
+        self._icon.run()
+
+    def _on_usage_update(self, data):
+        """Callback from fetcher thread — update icon + menu."""
+        with self._lock:
+            self.usage_data = data
+
+        pct = data.get("five_hour_pct", 0) if not data.get("error") else 0
+        try:
+            self._icon.icon = render_icon(pct)
+            # Force menu rebuild for dynamic text
+            self._icon.update_menu()
+        except Exception:
+            pass  # icon not yet visible
+
+        # Update tooltip
+        if data.get("error"):
+            self._icon.title = f"Claude Usage: {data['error']}"
+        else:
+            self._icon.title = f"Claude Usage: {data.get('five_hour_pct', 0)}%"
+
+    def on_refresh(self):
+        self.fetcher.refresh()
+
+    def on_set_interval(self, seconds):
+        self.fetcher.set_interval(seconds)
+
+    def on_session_key(self):
+        """Show a simple dialog to enter/update the session key."""
+        threading.Thread(target=self._session_key_dialog, daemon=True).start()
+
+    def _session_key_dialog(self):
+        root = tk.Tk()
+        root.withdraw()
+        current = config.get_session_key()
+        key = simpledialog.askstring(
+            "Claude Session Key",
+            "Paste your claude.ai sessionKey cookie value:",
+            initialvalue=current,
+            parent=root,
+        )
+        root.destroy()
+        if key is not None and key.strip():
+            config.set_session_key(key.strip())
+            self.fetcher.refresh()
+
+    def on_quit(self):
+        self.fetcher.stop()
+        self._icon.stop()
+
+
+def main():
+    logging.basicConfig(
+        level=logging.INFO,
+        format="%(asctime)s %(levelname)s %(name)s: %(message)s",
+    )
+    app = App()
+    app.run()