testsuite: output, comparison and algorithm-selection option coverage

testsuite: output, comparison and algorithm-selection option coverage

Breadth pass for options not yet exercised:

  output-options    output shape of --version/--help/-i/-n/--stats/
                    --out-format/--list-only/-q/--progress/-h/-8 (these control
                    output, not path handling, so they're checked for shape).
  compare           -c and -I catch a stealth change (same size+mtime, new
                    content) deep in the tree; --size-only skips a same-size
                    change; --modify-window absorbs a 1s mtime difference.
  compress-options  --compress-choice for every advertised compressor,
                    --compress-level, --skip-compress, --checksum-choice for
                    every advertised checksum, and --checksum-seed -- each a
                    clean byte-identical transfer at depth.

Green on master and under --protocol=29/30.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>