Windows: setup mcp fails with path quoting (C:\Program not recognized, v1.20.0)

## Summary
`firecrawl setup mcp` (firecrawl-cli **v1.20.0** on Windows) fails when spawning `npx.cmd` through `cmd.exe` because a spaced path is not quoted correctly:

```
'"C:\Program' is not recognized as an internal or external command,
operable program or batch file.
Error: Failed to configure Firecrawl MCP.
```

This reproduces for a single agent (`-a cursor`) and for `--agent all`. It is a CLI defect in `runClientCommand` / `escapeCmdArg` (see `dist/commands/setup.js`), not a user config issue.

## Environment
- OS: Windows 11
- firecrawl-cli: 1.20.0 (latest per `firecrawl doctor`)
- Node: v24.19.0 under `C:\Program Files\nodejs\` (path contains a space)
- Shell: PowerShell

## Steps to reproduce
1. `npm i -g firecrawl-cli@1.20.0`
2. `firecrawl setup mcp -g -a cursor -y --keyless`
3. Observe the `'"C:\Program' is not recognized` error

## Workaround (verified)
Bypass firecrawl's wrapper and call `add-mcp` directly from PowerShell/Node (which quotes `Program Files` correctly):

```
npx -y add-mcp@1.14.0 https://mcp.firecrawl.dev/v2/mcp --name firecrawl --transport http --global --all --yes
```

This successfully registered `https://mcp.firecrawl.dev/v2/mcp` on Cursor, Claude Code, Codex, Gemini CLI, VS Code/GitHub Copilot, Continue (manual YAML), and other detected agents.

## Expected
`firecrawl setup mcp` should configure the hosted MCP URL on Windows even when Node/npm live under `C:\Program Files\...`.

## Notes
`firecrawl doctor --query ...` could not file this via `/v2/support/ask` here because no API key is present in this shell (`Not authenticated`). Opening this issue instead.

Start in dist/commands/setup.js, focusing on runClientCommand and escapeCmdArg, then reproduce firecrawl setup mcp on Windows with Node under C:\Program Files\. Done means the command configures the hosted MCP URL for the requested agents without splitting the spaced executable path.

Written by the indexing model from the issue text.