Add multi-source overlap summary for v0.7.0 - #15

Summary

Add provider-neutral archive coverage intelligence on top of the provenance foundation merged in #14.

New CLI

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

Summary schema

• union_urls: normalized URLs seen by at least one selected source
• source_counts: unique normalized URLs per source
• exclusive_counts: normalized URLs seen only by one source
• shared_urls: normalized URLs seen by at least two sources
• overlap_urls: normalized URLs seen by every selected source
• complete: false when collection stops early or a source fails

Design

The analysis reuses core.run() in provenance mode. It does not duplicate provider, pagination, filtering, retry or normalization logic. URL membership is stored as compact 128-bit fingerprints.

--max-results counts per-source evidence records before aggregation.

Compatibility

• normal collection remains unchanged
• requires at least two selected sources
• cannot be combined with --provenance
• no live-target requests

Includes tests and documentation.

Part of #13.