Adds `marchwarden replay <trace_id>` to pretty-print a prior research
run from its JSONL trace file. Resolves the trace under
~/.marchwarden/traces/ by default; --trace-dir overrides for tests and
custom locations. Renders each step as a row with action, decision,
extra fields, and content_hash. Friendly errors for unknown trace_id
and malformed JSON lines.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
