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>

bin/arcodange

@@ -86,7 +86,8 @@ COMMANDS
     thirdparty                                     Create a client/supplier fiche
     invoice                                        Customer/supplier invoice + product/service lines
     payment                                        Record a règlement on a validated invoice
-    creditnote                                     Create an avoir (credit note) of a source invoice
+    creditnote                                     Create an avoir — customer or supplier (kind)
+    accounts                                       List bank accounts (id/label) to pick account_id
     write                <METHOD> <path> [body]    Raw host-guarded write
 
   promote                            Replay a reviewed change-set sandbox -> prod (ADR-0003)
@@ -285,6 +286,7 @@ EOF
       invoice)    exec "${SKILLS}/dolibarr-sandbox-write/scripts/invoice-create.sh"    "$@" ;;
       payment)    exec "${SKILLS}/dolibarr-sandbox-write/scripts/payment-record.sh"    "$@" ;;
       creditnote) exec "${SKILLS}/dolibarr-sandbox-write/scripts/creditnote-create.sh" "$@" ;;
+      accounts)   exec "${SKILLS}/dolibarr-sandbox-write/scripts/bank-accounts.sh"     "$@" ;;
       write)      exec "${SKILLS}/dolibarr-sandbox-write/scripts/dol-write.sh"          "$@" ;;
       help|-h|--help)
         cat <<'EOF'