feat: full auto-install chain for all platforms

- Wire ensure_claude_code() into cmd_update() — auto npm install if missing
- uclaude_install.sh: auto-install git, python3, curl via apt/dnf/yum/brew
- uclaude_update.bat: prereq checks with winget install suggestions
- uclaude_update.ps1: auto-install via winget (git, python, node)
- install_node(): macOS support via brew, RHEL/Fedora via rpm.nodesource
- Increased npm install timeout to 300s for slow connections

claude/uclaude_update.bat

@@ -6,11 +6,49 @@ setlocal enabledelayedexpansion
 set "SCRIPT_DIR=%~dp0"
 cd /d "%SCRIPT_DIR%\.."
 
-REM Pull latest artifacts
+REM ---- Check prerequisites ----
+
+where git >nul 2>&1
+if errorlevel 1 (
+    echo ERROR: git not found.
+    echo Install: winget install Git.Git
+    echo    or: https://git-scm.com/download/win
+    pause
+    exit /b 1
+)
+
+where python >nul 2>&1
+if errorlevel 1 (
+    where python3 >nul 2>&1
+    if errorlevel 1 (
+        echo ERROR: Python not found.
+        echo Install: winget install Python.Python.3.12
+        echo    or: https://www.python.org/downloads/
+        pause
+        exit /b 1
+    )
+)
+
+where node >nul 2>&1
+if errorlevel 1 (
+    echo WARNING: Node.js not found. Updater will attempt to guide you.
+    echo Install: winget install OpenJS.NodeJS
+    echo    or: https://nodejs.org/
+)
+
+REM ---- Pull latest artifacts ----
 git pull --quiet 2>nul
 
-REM Run updater
-python claude\uclaude_updater.py %*
+REM ---- Run updater ----
+
+REM Try python3 first, fallback to python
+where python3 >nul 2>&1
+if not errorlevel 1 (
+    python3 claude\uclaude_updater.py %*
+) else (
+    python claude\uclaude_updater.py %*
+)
+
 if errorlevel 1 (
     echo.
     echo If you see permission errors, run this script as Administrator.