Build and start the server app in the browser for peer-to-peer games #244

Which command is this feature request for?

build, start (and @nanoforge-dev/config)

Feature

Sub-issue of NanoForge-dev/Engine#284 (multiplayer without a game server). In peer-to-peer mode the game's server app runs in the host player's browser, so the CLI must build and start it differently.

Ideal solution or implementation

• @nanoforge-dev/config: add network: "dedicated" | "p2p" to the workspace config (default dedicated).
• nf build with network: "p2p": also build each server app with --target browser into the client's output, under server/. This runs after the client build, since that one resets the output.
• nf start with network: "p2p": add NANOFORGE_NETWORK_MODE=p2p to the env of both apps. The engine reads it.
• Dedicated mode is unchanged.

Other context

Engine side: @nanoforge-dev/network/server and @nanoforge-dev/ecs/server pick their browser builds on their own. In p2p mode the Bun server process only does WebRTC signaling, on LISTENING_TCP_PORT.