Add a custom connector called SEC Stock Signals.

Read the brief in muse-connector.md first.

This connector is retrieval-only public SEC 8-K event statistics.
It is not a broker and not investment advice.

No API key. Do not ask me for credentials.

Tools (GET JSON):
- /api/v1/capabilities
- /api/v1/verdict
- /api/v1/integrity
- /api/v1/families?name=
- /api/v1/ticker/{TICKER}

When it works, save it as SEC Stock Signals.
Do not recommend buy, sell, or hold.
Do not treat information-gap scores as a product.
If a ticker is unknown, say it is outside the study. Do not invent events.
