codeSplitter: Dependency doctor: repo health page, your versions vs latest #860

Part of #859.

A page per repo that shows how its dependencies stand: what the repo pins compared with what the registry has.

• One row per package: your version · latest · how far behind (versions and days) · vulnerability badge · 🪏 watch state
• A single health score for the repo up top
• Built on the doctor's existing report (src/deps.ts Report) and the supply-chain watch hits. Little new data is needed.
• UI: very minimal, icons and numbers with the words as tooltips, so the main view barely needs translating

Done when an owner can open it from the repo page and see each package's distance from latest at a glance.