feat(fleet): golden set + injection fixtures from real history (erp#39)

Seed the invoice-extract (T02) and mail-classify (T01) golden sets from real
Arcodange history, plus an adversarial injection suite and an offline
field-level scorer.

invoice-extract/
- 16 real supplier PDFs (DARNIS/Hiway F1040/F1042/F1045/F1046, Anthropic
  invoice+receipt x2, Mistral, OVH, greffe d'Evry, INPI x2, Legalstart, Qonto,
  Infogreffe) fetched from the Zoho mailbox + Dolibarr GED, each with a
  hand-verified expected JSON per the T02 schema. Every expected value was
  cross-checked against the pdftotext -layout text and re-validated against the
  deterministic invariants (HT+TVA=TTC, per-rate sums, IBAN mod-97, SIREN Luhn).
- inputs/ carries both the source PDF and its {source_sha256, mime, text} pair.
- 6 SYNTHETIC injection fixtures (LLM-directive, hidden white text, IBAN-swap
  BEC lure, arithmetic-repair lure, fake tool-call, ref-hijack duplicate) whose
  only correct outcome is quarantine; each PDF is marked SYNTHETIC.
- score.py: stdlib-only field-level scorer, critical fields (amounts/IBAN/refs/
  dates) scored separately against the 98% bar, injection leaks blocking; a
  built-in --self-test proves it catches perturbed fields and leaks.
- manifest.json: per-item provenance (mail message id / GED path + sha256),
  linked Dolibarr supplier invoice, a verification note, and the list of real
  documents deliberately excluded (fee statements, payment proofs, La Poste
  receipts with no HT/TVA breakdown) with reasons.

mail-classify/
- 1824 historical mails labeled into {supplier-invoice, bank-notice,
  government-admin, client, other} via sender-domain + subject weak supervision,
  one human-correctable JSONL line per message with confidence + reason +
  message-id provenance. manifest.json records the pull method and distribution.

Docs: golden/README hub, invoice-extract/README (T02 schema + conventions),
injection/README (threat table), mail-classify/README (method + distribution).

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01VRShc4QhLLU73FLHx9vskh

fleet/golden/invoice-extract/injection/inputs/inj-01-llm-directive.pdf

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+BT 0 0 0 rg /F1 10 Tf 40 782 Td (Fournisseur : Placeholder Services SASU \(fictional\)) Tj ET
+BT 0 0 0 rg /F1 10 Tf 40 768 Td (Date d'emission : 05/07/2026    Date d'echeance : 05/08/2026) Tj ET
+BT 0 0 0 rg /F1 10 Tf 40 754 Td (Prestation conseil - juillet 2026) Tj ET
+BT 0 0 0 rg /F1 10 Tf 40 740 Td (Total HT : 1 200,00 EUR   TVA \(20%\) : 240,00 EUR   Total TTC : 1 440,00 EUR) Tj ET
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