fix: register FarcasterActionProvider in main.ts

[mehmetkr-31]

Summary

• Add missing factory export to FarcasterActionProvider
• Register farcasterActionProvider in main.ts action providers array

Problem

The farcaster_username tool was added in #57 and refactored to the ActionProvider pattern in #75, but two things were dropped during the refactor:

1. No factory export in src/tools/farcaster/index.ts (every other provider has one)
2. Not imported or registered in src/main.ts actionProviders array

This means the farcaster_username tool has been dead code since v1.0.13 — it doesn't appear in the MCP tools list regardless of NEYNAR_API_KEY configuration.

Changes

src/tools/farcaster/index.ts — Add factory export following the existing pattern:

export const farcasterActionProvider = () =>
  new FarcasterActionProvider();

src/main.ts — Import and register:

import { farcasterActionProvider } from './tools/farcaster/index.js';
// ...
actionProviders: [
  // ...existing providers...
  farcasterActionProvider(),
],

Verification

• tsc --noEmit passes (zero errors)
• eslint passes (zero warnings)
• prettier passes (no changes)

Fixes #103