Add a project quick-start view for repos without sessions

[jongio]

Problem

Dispatch only shows projects that already have Copilot sessions. If a developer wants to start work in a repo with no recent session, they must leave Dispatch, change directories, and run Copilot manually.

Proposed solution

Add a project quick-start view that scans configured project roots for git repositories and shows New session rows for repos without a recent Copilot session. Pressing Enter on one of these rows should launch Copilot in that folder using the existing launch mode, terminal, shell, agent, model, and yolo settings. Keep the first version simple: configured roots, git repo detection, and launch from the repo root.

User impact

Developers can use Dispatch as the entry point for both resuming old work and starting new work. This matches how project switchers and session pickers are used in terminal workflows.

Acceptance criteria

• Settings can store one or more project root directories to scan.
• The session list can include New session rows for git repos under those roots.
• Launching a New session row starts Copilot in the repo root using existing launch settings.
• Existing session rows keep their current behavior.
• Tests cover repo discovery, config parsing, and launch command construction.

Complexity & priority

Complexity: L | Priority: 4