feat(evidence): agent-consultable attested-characterization tool + citeable journal articles

- consult_attested_characterization (MIKE_CONSULT_ATTESTATIONS=1): a read-only
  citator tool returning up to 3 attested characterizations of a cited case,
  ranked scc_journal_first (court-level band, occurrence count within band,
  then recency; two case slots then journal), each with a registered
  evidence_id and an actionable follow_up pulling the citing case (a2aj_fetch)
  or journal article (public_legal_source_fetch, with a page-lookup hint).
- StandsForCandidate now carries sourceArticleId + citingUrl so follow-ups and
  rendered deep links resolve.
- public_legal_source_fetch (provider journal) registers a passage-scope
  public-journal-v1 receipt: the pulled article becomes citeable by
  submit_grounded_answer (the attestation receipts already were).
- Render surfaces the "as characterized by/in ..." attribution and deep-links
  case attestations to the exact prose in the citing case via text-fragment
  pinpoint.
- Tests cover rank ordering, the tool surface, dispatcher registration, and
  the render (93 pass).

Also in this commit (same tree): the concurrent silo'd derived-section-index
integration (localAssistantTools / lab-beaver-arm / upstreamMikeBenchmarkSurface)
and the Harvey LAB launchpad generator (tools/generate_launchpad.py + smoke
test). The generated launchpad.html/materials.json are gitignored - regenerable,
and the 86 MB materials JSON embeds already-tracked corpus text.

Co-Authored-By: Claude <noreply@anthropic.com>