feat: define and implement server distribution strategy

[jamilagibson]

Context

The WebSocket server currently runs via node server/server.js. For npm packaging, developers need a defined way to start it. Three options exist:

Options

1. Bundled CLI — npx reactime-native starts the server (simplest DX)
2. Separate package — npm install -g reactime-native-server (cleaner separation)
3. Auto-started by agent — server starts when initReactimeNative() is called (most magical, hardest to implement)

Decision needed

The team needs to agree on option 1, 2, or 3 before implementation begins. This decision gates the entire v0.3.0 packaging milestone.

Acceptance criteria

• Distribution strategy agreed and documented in CLAUDE.md engineering decision log
• Server startable via the agreed mechanism in a fresh install
• README.md reflects the correct start command