Redacted excerpt; full evidence withheld.

$ cd <host-path> && git log -1 --format=%H 2>/dev/null; ls -la; cat README.md 2>/dev/null | head -200
exit: 0
XCEL_OUTPUT_ROOTS` set to a directory that already exists

`excel_write_csv` stays its own tool so the read tools can be annotated
read-only. Folding the write into `excel_read_table` would make that tool a
writer on some calls, and the annotation is per tool, not per call.

Optional caps: `EXCEL_MAX_FILE_BYTES` (default 26214400), `EXCEL_MAX_ROWS`
(default 5000), `EXCEL_MAX_COLUMNS` (default 128), `EXCEL_MAX_SCAN_ROWS`
(default 100000). Values above the built-in ceilings are clamped. See
[docs/SECURITY.md](docs/SECURITY.md).
[excerpt truncated]