fix(hooks): add WSL desktop notification support via PowerShell + BurntToast

Adds WSL (Windows Subsystem for Linux) desktop notification support to the
existing desktop-notify hook. The hook now detects WSL, finds available
PowerShell (7 or Windows PowerShell), checks for BurntToast module, and
sends Windows toast notifications.

New functions:
- isWSL(): detects WSL environment
- findPowerShell(): finds PowerShell 7 or Windows PowerShell on WSL
- isBurntToastAvailable(): checks if BurntToast module is installed
- notifyWindows(): sends Windows toast notification via BurntToast

If BurntToast is not installed, logs helpful tip for installation.
Falls back silently on non-WSL/non-macOS platforms.

scripts/hooks/desktop-notify.js

@@ -3,9 +3,11 @@
  * Desktop Notification Hook (Stop)
  *
  * Sends a native desktop notification with the task summary when Claude
- * finishes responding.  Currently supports macOS (osascript); other
- * platforms exit silently.  Windows (PowerShell) and Linux (notify-send)
- * support is planned.
+ * finishes responding.  Supports:
+ *   - macOS: osascript (native)
+ *   - WSL: PowerShell 7 or Windows PowerShell + BurntToast module
+ *
+ * On WSL, if BurntToast is not installed, logs a tip for installation.
  *
  * Hook ID : stop:desktop-notify
  * Profiles: standard, strict
@@ -19,6 +21,60 @@ const { isMacOS, log } = require('../lib/utils');
 const TITLE = 'Claude Code';
 const MAX_BODY_LENGTH = 100;
 
+/**
+ * Check if running on WSL (Windows Subsystem for Linux).
+ */
+function isWSL() {
+  if (process.platform !== 'linux') return false;
+  try {
+    return require('fs').readFileSync('/proc/version', 'utf8').toLowerCase().includes('microsoft');
+  } catch {
+    return false;
+  }
+}
+
+/**
+ * Find available PowerShell executable on WSL.
+ * Checks PowerShell 7 first, then falls back to Windows PowerShell.
+ * Returns { path, version } or null if none available.
+ */
+function findPowerShell() {
+  if (!isWSL()) return null;
+
+  const candidates = [
+    '/mnt/c/Program Files/PowerShell/7/pwsh.exe',      // PowerShell 7
+    '/mnt/c/Windows/System32/WindowsPowerShell/v1.0/powershell.exe', // Windows PowerShell
+  ];
+
+  for (const path of candidates) {
+    try {
+      const result = spawnSync(path, ['-Command', '$PSVersionTable.PSVersion.Major'],
+        { stdio: ['ignore', 'pipe', 'ignore'], timeout: 3000 });
+      if (result.status === 0) {
+        const version = parseInt(result.stdout.toString().trim(), 10);
+        return { path, version };
+      }
+    } catch {
+      // continue
+    }
+  }
+  return null;
+}
+
+/**
+ * Check if BurntToast module is available on the given PowerShell path.
+ */
+function isBurntToastAvailable(pwshPath) {
+  try {
+    const result = spawnSync(pwshPath,
+      ['-Command', 'Import-Module BurntToast -ErrorAction Stop; $true'],
+      { stdio: ['ignore', 'pipe', 'ignore'], timeout: 5000 });
+    return result.status === 0;
+  } catch {
+    return false;
+  }
+}
+
 /**
  * Extract a short summary from the last assistant message.
  * Takes the first non-empty line and truncates to MAX_BODY_LENGTH chars.
@@ -53,20 +109,45 @@ function notifyMacOS(title, body) {
   }
 }
 
-// TODO: future platform support
-// function notifyWindows(title, body) { ... }
-// function notifyLinux(title, body) { ... }
+/**
+ * Send a Windows Toast notification via PowerShell BurntToast.
+ * Used when running under WSL to show notification on Windows desktop.
+ */
+function notifyWindows(pwshPath, title, body) {
+  const safeBody = body.replace(/'/g, "''");
+  const safeTitle = title.replace(/'/g, "''");
+  const command = `Import-Module BurntToast; New-BurntToastNotification -Text '${safeTitle}', '${safeBody}'`;
+  const result = spawnSync(pwshPath, ['-Command', command], { stdio: 'ignore', timeout: 5000 });
+  if (result.error || result.status !== 0) {
+    log(`[DesktopNotify] BurntToast failed (exit ${result.status}): ${result.error ? result.error.message : result.stderr?.toString()}`);
+  }
+}
 
 /**
  * Fast-path entry point for run-with-flags.js (avoids extra process spawn).
  */
 function run(raw) {
   try {
-    if (!isMacOS) return raw;
-
     const input = raw.trim() ? JSON.parse(raw) : {};
     const summary = extractSummary(input.last_assistant_message);
-    notifyMacOS(TITLE, summary);
+
+    if (isMacOS) {
+      notifyMacOS(TITLE, summary);
+    } else if (isWSL()) {
+      // WSL: try PowerShell 7 first, then Windows PowerShell
+      const ps = findPowerShell();
+      if (ps && isBurntToastAvailable(ps.path)) {
+        notifyWindows(ps.path, TITLE, summary);
+      } else if (ps) {
+        // PowerShell exists but no BurntToast module
+        log('[DesktopNotify] Tip: Install BurntToast module to enable notifications:');
+        log(`[DesktopNotify]   ${ps.path} -Command "Install-Module -Name BurntToast -Scope CurrentUser"`);
+      } else {
+        // No PowerShell found
+        log('[DesktopNotify] Tip: Install BurntToast in PowerShell for notifications:');
+        log('[DesktopNotify]   https://github.com/microsoft/BurntToast');
+      }
+    }
   } catch (err) {
     log(`[DesktopNotify] Error: ${err.message}`);
   }