fix(cli): honor --no-headers flag with --fmt/--table output

[CrepuscularIRIS]

Summary

Fixes #566

The --no-headers flag was silently ignored when combined with --fmt or --table. Headers appeared in the output regardless.

Root Cause

The --no-headers flag was only checked in the CSV/TSV output branch (line 243). When --fmt or --table was used, tabulate.tabulate() was always called with headers=headers, bypassing the flag entirely. This affected both the tables command (line 240) and the query/_execute_query path (line 2148).

Changes

• sqlite_utils/cli.py: Pass headers=() if no_headers else headers to both tabulate.tabulate() call sites. tabulate natively supports headers=() for suppressing header display.
• tests/test_cli.py: Added test_output_table_no_headers (parametrized over plain and simple formats) and test_query_fmt_no_headers (verifies the query command path).

Testing

• Full test suite passes (1039 passed, 16 skipped, 0 failures)
• New tests fail when fix is reverted (verified)
• No regressions from baseline (1036 → 1039 with 3 new tests)

python -m pytest tests/test_cli.py::test_output_table_no_headers tests/test_cli.py::test_query_fmt_no_headers -v

Notes

Chose to make --no-headers work with --fmt rather than raising an error, since tabulate supports headerless output cleanly via headers=(). This keeps --no-headers consistent across all output modes (CSV, TSV, and tabulate formats).

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📚 Documentation preview 📚: https://sqlite-utils--729.org.readthedocs.build/en/729/