The hub is born

A new hub command serves an embedded web app for boards, runs, costs and configuration.

Added

trau serve starts a hub with an embedded web app
Live agent transcripts and repo events stream to the browser
A board of repos and runs, with a per-phase token and cost table on each run
A costs page with daily, per-repo and per-phase rollups, a lessons browser and a config editor
PRD drafting with publishing to Linear and Jira
An away recap and browser notifications for run events