rustybuns drift: show where the account no longer matches the stack #2236

Alchemy has alchemy drift and Drift.detect/plan/repair (docs): it re-reads the live account and reports resources changed or deleted outside the stack (dashboard edits, wrangler deploys). rustybuns plan only diffs config against state, so we never see this today.

Add rustybuns drift, read-only by default, using the generated stack. Leave --repair behind an explicit flag plus confirmation. Best done after the beta.84 bump.

Map: notes/ALCHEMY.md (#2234).