feat: Windows native support via Git Bash

- Add scripts/install.cmd batch wrapper for CMD users (delegates to install.ps1)
- Add _find_shell() in local.py: detects Git Bash on Windows via
  HERMES_GIT_BASH_PATH env var, shutil.which, or common install paths
  (same pattern as Claude Code's CLAUDE_CODE_GIT_BASH_PATH)
- Use _find_shell() in process_registry.py for background processes
- Fix hermes_cli/gateway.py: use wmic instead of ps aux on Windows,
  skip SIGKILL (doesn't exist on Windows), fix venv path
  (Scripts/python.exe vs bin/python)
- Update README with three install commands (Linux/macOS, PowerShell, CMD)
  and Windows native documentation

Requires Git for Windows, which bundles bash.exe. The terminal tool
transparently uses Git Bash for shell commands regardless of whether
the user launched hermes from PowerShell or CMD.

tools/process_registry.py

@@ -42,6 +42,7 @@ import time
 import uuid
 
 _IS_WINDOWS = platform.system() == "Windows"
+from tools.environments.local import _find_shell
 from dataclasses import dataclass, field
 from pathlib import Path
 from typing import Any, Dict, List, Optional
@@ -148,7 +149,7 @@ class ProcessRegistry:
             # Try PTY mode for interactive CLI tools
             try:
                 import ptyprocess
-                user_shell = os.environ.get("SHELL") or shutil.which("bash") or "/bin/bash"
+                user_shell = _find_shell()
                 pty_env = os.environ | (env_vars or {})
                 pty_env["PYTHONUNBUFFERED"] = "1"
                 pty_proc = ptyprocess.PtyProcess.spawn(
@@ -186,7 +187,7 @@ class ProcessRegistry:
         # Standard Popen path (non-PTY or PTY fallback)
         # Use the user's login shell for consistency with LocalEnvironment --
         # ensures rc files are sourced and user tools are available.
-        user_shell = os.environ.get("SHELL") or shutil.which("bash") or "/bin/bash"
+        user_shell = _find_shell()
         # Force unbuffered output for Python scripts so progress is visible
         # during background execution (libraries like tqdm/datasets buffer when
         # stdout is a pipe, hiding output from process(action="poll")).