Function renderDelta

renderDelta(delta: RunDelta): string
Renders a RunDelta as the lines a run report appends.
Parameters
- delta: RunDelta
Returns string
Remarks
One line per fact, labeled, so a reader scans the labels: what was written and what it replaced, the formulas with their results, what moved, what reads the write, the errors, and what sits over it that is not a cell.
Example
```
Changed:      Sheet1!H7:H38 — 32 formulas, 0 populated cells replaced
  Sheet1!H7:H38  =B7*C7  → 12, 15, 18 … 90 (32 cells)
Structure:    Sheet1!5:7 rows inserted
Dependents:   212 cells on 2 sheets — Sheet1!K7:K38, Summary!B4:B9
Errors:       Sheet1!K9:K12 #VALUE! (4)
```