arrowbricks v6.2.0

Why TSV: with the shipped renderer on ten sample result sets, TSV used 28% fewer
o200k_base tokens than 6.1's Markdown table (12% fewer than the new unpadded
Markdown), decoded back losslessly for all 14,810 cells, and could not be broken
by any Unicode character. In 12 blind reader runs (Haiku and Sonnet, 82
questions) the layouts scored the same within noise (TSV 97.6%, new Markdown
97.6%, 6.1 Markdown 98.8%), so TSV is cheaper without being less accurate; the
benchmark does not show it is more accurate. Method, numbers and caveats:
benchmarks/2026-10-12-agent-output-format.md.

• Add output_format to DatabricksClient.query_agent and --format to the
  CLI: "tsv" (the new default) or "markdown" (typed as the exported
  arrowbricks.AgentFormat literal). TSV prints a name:Type
  header and one tab-separated line per row. Backslash, tab, newline and
  carriage return in values become \\, \t, \n and \r, SQL NULL is \N
  and the empty string is an empty field, so a cell can never contain a raw
  delimiter.
• Behavior change: the default output is now TSV, and the Markdown table no
  longer pads cells with spaces (|a (Int64)|b (Utf8)|, separator |-|-|), 19% fewer tokens.
  Pass output_format="markdown" / --format markdown for the table. Both
  layouts end with the same completeness footer and share the byte budget.
• The CLI recognises an error by parsing it as a JSON object, so a column named
  like {x} no longer sends a successful TSV result to stderr.