[Desktop] Allow setting a default project folder for new sessions

Problem

In the Claude Code desktop app (Windows 11, v1.40609.0), every new session starts with "No folder" and lands in a temporary scratch workspace. Users who work mostly in one repo have to select the project folder manually every single time.

Expected

A way to make new sessions open in a chosen folder by default — e.g. a "default project folder" setting, or an option to reuse the folder of the most recent session.

Current workarounds

• Pick from the recent-folders list (still a manual step every session)
• Resume an old session in that repo
• Launch claude from a terminal already in the repo (bypasses the desktop app entirely)

There is no setting for this in config.json.