Wire amendment, deadline, term-drift, and bilingual tools into chat

Four deterministic capabilities become library tools:
- library_apply_amendment: dry-run consolidation of an amending
  instrument against a source document - typed op receipts, refusals,
  hard failures, recompile verification; never writes a version
- library_deadline: traced deadline arithmetic (Interpretation Act
  ss. 26-28, business days, computed holiday tables CA/ON/BC/QC/US);
  schema tells the model to NEVER do calendar math in prose
- library_term_drift: deal-stack defined-term divergence report
- library_bilingual_concordance: EN/FR anchor concordance gate for
  equally-authentic bilingual instruments

All matter-allowlist-checked, all report-only. tsc clean; existing
localAssistantTools tests 8/8.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018bhP89cYSdEEjHNPnxacns