feat: give synopsis get_hints tool to fetch relevant developer hints from local context store

[ahau-square]

Beginning sketch of how Goose might retrieve context from a local context store via an additional tool call.

The local context store referenced is an interface to LanceDB as defined here: https://github.com/squareup/goose-context-store

The general idea is that based on a new task, Goose will first fetch relevant hints based on text and semantic queries to the local context store, and append those to its existing .goosehints as part of the system prompt.