feat(skills,cli): supplier avoirs + banque lire (bank-account discovery)

The two V9 follow-ups, both proven live on the sandbox.

- creditnote-create.sh: `kind:"supplier"` makes an avoir fournisseur on
  /supplierinvoices (type=2 + fk_facture_source, carries ref_supplier); default
  customer path unchanged. Proven: customer AVC002 (-240) + supplier AVF2026001
  (-144, ref_supplier carried, linked to source, validated).
- bank-accounts.sh + `arcodange sandbox accounts`: list bank accounts (id/label/
  bank) so a payment can pick its account_id. Needs `banque lire` (rights 111),
  now added to the provisioner's WRITE_IDS so fresh runs include it; the existing
  ai_agent_sandbox user was granted it live. GET /bankaccounts now returns the 3
  accounts (QONTO, WISE EURO, Compte Courant Asso).
- SKILL.md: supplier-avoir example + accounts helper + updated banque-lire note.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

test/provisionSandbox.ts

@@ -38,6 +38,7 @@ import userSetup from "./scripts/admin/userSetup.ts";
     societe contact:   lire=281,  creer=282
     fournisseur:       lire=1181, facture lire=1231, facture creer=1232
     produit:           lire=31,   creer=32
+    banque:            lire=111
 */
 const WRITE_IDS = [
   11, // facture lire
@@ -54,6 +55,7 @@ const WRITE_IDS = [
   1232, // fournisseur facture creer
   31, // produit lire
   32, // produit creer
+  111, // banque lire — list bank accounts (GET /bankaccounts) to pick account_id
 ];
 
 const KEY_FILE = ".ai_agent_sandbox.key";