Fix Xcode MCP spam security prompts in Codex/Claude Code — mcp-proxy

Problem

Xcode 26.3's MCP bridge (xcrun mcpbridge) uses stdio transport which only supports a single connection. Codex App spawns a new mcpbridge process per agent/tool call, triggering a macOS security approval dialog every time. Affects Claude Code multi-agent setups too.

Fix: Route all agents through a single persistent mcp-proxy

# 1. Install mcp-proxy globally
npm install -g mcp-proxy

# 2. Start one persistent mcpbridge behind the proxy (run in background)
mcp-proxy --port 9876 -- xcrun mcpbridge &

# 3. Register the proxy URL with Codex instead of the raw stdio bridge
codex mcp remove xcode 2>/dev/null
codex mcp add --url http://localhost:9876/mcp xcode-proxy

For Claude Code (~/.claude/settings.json):

{
  "mcpServers": {
    "xcode": {
      "url": "http://localhost:9876/mcp"
    }
  }
}

Also: Update Xcode to 26.3 RC2 (build 17C528) — RC1 had MCP error -32600 that caused agents to retry and re-spawn connections in a loop, amplifying the spam.

Root cause: Xcode triggers a per-connection TCC authorization prompt. CLI reuses one connection → one prompt. The App spawns connections per-agent → spam. mcp-proxy multiplexes multiple agents over a single persistent connection.