feat(shell): add --force-shell option to override shell selection

- Add --force-shell CLI argument with choices [bash, zsh, sh]
- Set HANZO_MCP_FORCE_SHELL environment variable when option is used
- Modified BashTool, ZshTool, and ShellTool to respect the env var
- Allows users to force all shell operations to use a specific shell
  even when AI requests a different one

Example usage in ~/.claude.json:
  "args": ["hanzo-mcp", "--force-shell", "zsh"]

Bumps version to 0.9.19

pkg/hanzo-mcp/hanzo_mcp/cli.py

@@ -199,6 +199,14 @@ def main() -> None:
         help="Timeout specifically for AST operations. Supports: 2min, 5m, 120s, 30sec, 1.5h",
     )
 
+    _ = parser.add_argument(
+        "--force-shell",
+        dest="force_shell",
+        choices=["bash", "zsh", "sh"],
+        default=None,
+        help="Force all shell tools (bash, zsh, shell) to use this shell (default: use requested shell)",
+    )
+
     _ = parser.add_argument(
         "--disable-write-tools",
         dest="disable_write_tools",
@@ -307,6 +315,10 @@ def main() -> None:
         ast_timeout = _parse_timeout_arg(args.ast_timeout)
         os.environ["HANZO_MCP_AST_TIMEOUT"] = str(ast_timeout)
 
+    # Set force shell environment variable
+    if hasattr(args, "force_shell") and args.force_shell:
+        os.environ["HANZO_MCP_FORCE_SHELL"] = args.force_shell
+
     # Cast args attributes to appropriate types to avoid 'Any' warnings
     name: str = cast(str, args.name)
     install: bool = cast(bool, args.install)

pkg/hanzo-mcp/hanzo_mcp/tools/shell/bash_tool.py

@@ -59,7 +59,15 @@ bash "npm run dev" --cwd ./frontend  # Auto-backgrounds if needed"""
 
     @override
     def get_interpreter(self) -> str:
-        """Get the bash interpreter."""
+        """Get the bash interpreter.
+        
+        Respects HANZO_MCP_FORCE_SHELL environment variable to override.
+        """
+        # Check for forced shell override
+        force_shell = os.environ.get("HANZO_MCP_FORCE_SHELL")
+        if force_shell:
+            return force_shell
+        
         if platform.system() == "Windows":
             # Try to find bash on Windows (Git Bash, WSL, etc.)
             bash_paths = [

pkg/hanzo-mcp/hanzo_mcp/tools/shell/zsh_tool.py

@@ -66,7 +66,15 @@ zsh "npm run dev" --cwd ./frontend  # Auto-backgrounds if needed"""
 
     @override
     def get_interpreter(self) -> str:
-        """Get the zsh interpreter path."""
+        """Get the zsh interpreter path.
+        
+        Respects HANZO_MCP_FORCE_SHELL environment variable to override.
+        """
+        # Check for forced shell override
+        force_shell = os.environ.get("HANZO_MCP_FORCE_SHELL")
+        if force_shell:
+            return force_shell
+            
         if platform.system() == "Windows":
             # Try to find zsh on Windows (WSL, Git Bash, etc.)
             zsh_paths = [
@@ -144,7 +152,15 @@ class ShellTool(BaseScriptTool):
         self._best_shell = self._detect_best_shell()
 
     def _detect_best_shell(self) -> str:
-        """Detect the best available shell."""
+        """Detect the best available shell.
+        
+        Respects HANZO_MCP_FORCE_SHELL environment variable to override.
+        """
+        # Check for forced shell override first
+        force_shell = os.environ.get("HANZO_MCP_FORCE_SHELL")
+        if force_shell:
+            return force_shell
+            
         # Check for zsh first
         if shutil.which("zsh"):
             # Also check if .zshrc exists

pkg/hanzo-mcp/pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "hanzo-mcp"
-version = "0.9.18"
+version = "0.9.19"
 description = "The Zen of Hanzo MCP: One server to rule them all. The ultimate MCP that orchestrates all others."
 readme = "README.md"
 requires-python = ">=3.12"