Add a Markdown/CSV export of the ranked-config table

[AshwinUgale]

The problem / use case

Context: run already writes full results (--json) and a self-contained report
(--html). A plain table export is the missing lightweight format.

What: Add --markdown out.md (and/or --csv out.csv) that writes the ranked configs
with hit@k / MRR (+ CIs) — the same rows the HTML report ranks.

Acceptance:

• --markdown / --csv produce the ranked table; values match the HTML report
• a test in tests/test_cli.py; CHANGELOG.md updated

Pointers: pull the ranked rows from the same place report.py builds the HTML table.

Proposed idea

Besides --json and --html, let a run emit the ranked-configurations table as Markdown or CSV, so results drop straight into a PR comment, README, or spreadsheet.