Add source-aware provenance mode for v0.7.0 - #14

Summary

Start the v0.7.0 multi-source intelligence work with an opt-in provenance mode.

New behavior

wayparam -d example.com \
  --source wayback,commoncrawl \
  --provenance \
  --format jsonl

With --provenance, the same normalized endpoint can be emitted once per selected archive source. Repeated variants inside the same source are still deduplicated.

Compatibility

• default behavior is unchanged
• global cross-provider dedup remains the default
• --provenance is JSONL-only because TXT cannot carry source identity
• provenance mode cannot be mixed with the existing Wayback-only historical analysis modes

Coverage

Adds core and CLI regression tests plus README/manpage/changelog documentation.

Part of #13.