codeSplitter: Dependency doctor: owner-built on-fail chain (retry, AI fix, web search, hold, roll back, alert) #861

Part of #859.

Today an update that breaks the tests goes to the fixer agent (if one is set) and is otherwise dropped. Instead, let the owner build an ordered on-fail chain out of icon steps:

🔁 retry alone → 🤖 AI fix (existing fixer) → 🔎 AI web search for known breakage (e.g. "pkg@x + vite@y") → 📌 hold back → ↩️ roll back → 🔔 alert

• The owner reorders and toggles the steps, and the chain stops at the first one that succeeds
• Limits over the whole chain: tries, minutes, and a dollar cap for the AI steps
• The run report says which step resolved each update or gave up on it
• The AI steps use the owner's connected AI (the same harness choice as fix_with)