fix: Force bash for SSH commands and suppress known_hosts warnings

- Add UserKnownHostsFile=/dev/null to prevent write errors on read-only .ssh
- Wrap all SSH commands with 'bash -c' for fish shell compatibility on remote

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

haproxy_mcp/ssh_ops.py

@@ -21,6 +21,7 @@ def _ssh_base_cmd() -> list[str]:
     cmd = [
         "ssh",
         "-o", "StrictHostKeyChecking=no",
+        "-o", "UserKnownHostsFile=/dev/null",
         "-o", "BatchMode=yes",
         "-o", "ConnectTimeout=10",
         "-p", str(SSH_PORT),
@@ -45,7 +46,7 @@ def remote_exec(command: str, timeout: int = SUBPROCESS_TIMEOUT) -> subprocess.C
         subprocess.TimeoutExpired: If command times out
         OSError: If SSH command fails to execute
     """
-    ssh_cmd = _ssh_base_cmd() + [command]
+    ssh_cmd = _ssh_base_cmd() + ["bash", "-c", command]
     logger.debug("SSH exec: %s", command)
     return subprocess.run(
         ssh_cmd,
@@ -89,11 +90,10 @@ def remote_write_file(path: str, content: str) -> None:
     Raises:
         IOError: If write fails
     """
-    # Escape content for shell, use heredoc via stdin
     ssh_cmd = _ssh_base_cmd()
-    # Atomic write: write to temp file, then rename
+    # Atomic write: write to temp file, then rename (force bash for compatibility)
     remote_script = f"tmpf=$(mktemp {path}.tmp.XXXXXX) && cat > \"$tmpf\" && mv \"$tmpf\" {path}"
-    ssh_cmd.append(remote_script)
+    ssh_cmd.extend(["bash", "-c", remote_script])
 
     logger.debug("SSH write: %s (%d bytes)", path, len(content))
     result = subprocess.run(