Calibrate board mutations

Prepare an evidence-backed estimate ledger, then delegate shared-state authorization to preflight-mutations. This skill reads and calculates. The workflow that owns the board performs the writes.

1. Fix the eligible scope

Resolve the board, estimate field, candidate item IDs, requester identity, and governing ownership policy from current board data. Include only items the policy permits. Treat unassigned, other-owned, and ambiguous items as read-only unless the user explicitly names and authorizes them.

Create one ledger in the existing authorized artifact that owns the batch:

### Estimate calibration

- **Board / field:** <stable board ID and estimate field ID>
- **Eligible scope:** <owner rule and exact candidate IDs>
- **Unit / scale:** <agent-assisted hours, person-hours, points, allowed values, rounding>
- **Calibration source:** <applicable policy or 3-5 user-approved anchors>
- **Sample approval:** <approval source or pending>
- **Umbrella rule:** <classification and aggregation rule>