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Fix #40: add --break-after to dump an intermediate pipeline step The REPL already exposes intermediate stages via :step / :breakpoint, but there was no non-interactive way to inspect a partial pipeline (libdivvun's modes files). Add `run --break-after <step>` (-b): it runs the pipeline up to the named step using a capturing tap, prints that step's raw output, and stops. Unknown step names error out with the list of available steps. Output respects the same colour rules as the final result (plain when piped). Closes the gap left by the interactive-only stepping.