Excel connector

Query an .xlsx workbook with SQL. Each sheet is loaded into an in-memory DuckDB (NaN → NULL) and becomes a view, so spreadsheets answer the same SQL as a real database.

# sources.yaml
book:
  type: excel
  path: data/report.xlsx
  header: true         # first row is the header (default true)
  sheets:              # optional: limit/rename which sheets load
    - Sheet1
    - Summary

Key	Purpose
`path`	Path to the `.xlsx` file.
`sheets`	Which sheets to load (default: all).
`header`	Boolean: is the first row the column header? (default `true`). Set `false` to auto-name columns `col0…colN`.

Then SELECT … FROM Sheet1. Install: uv add 'dashdown-md[excel]' (openpyxl).