feat(mcp): gnubok_reconcile_residual stages residual booking + link on a bank account (#1872)

The residual door existed for the page and the v1 API (#1862) but not for
agents: an MCP client that found a 10 kr bank fee between a selection and its
verifikat had to hand the last step back to the user. gnubok_reconcile_residual
dry-runs lib/reconciliation/residual.ts at stage time (so zero / cap /
direction / skattekonto refusals surface immediately), stages a
reconciliation_residual operation with the would-book verifikat as the
preview, and commitReconciliationResidual links and books on approval.

Risk 'medium' (one typed verifikat bounded by RESIDUAL_MAX_AMOUNT, undone by
storno + unmatch); scope transactions:write like the v1 route. The op type
is added to the pending_operations CHECK (NOT VALID + VALIDATE pair, list
verified against the live prod constraint 2026-08-25), and the tool joins
the reconcile_month / close_period loadouts and the reconcile-month skill.

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

types/index.ts

@@ -2494,6 +2494,8 @@ export type PendingOperationType =
   | 'reconciliation_unmatch'
   // Sign-off "avstämt t.o.m. <datum>" on one account (account_reconciliations row).
   | 'reconciliation_signoff'
+  // Book the remainder of a bank selection as a fee/interest/rounding verifikat and link it.
+  | 'reconciliation_residual'
   // PR5: Skatteverket filing via MCP. Commit = "send for BankID signing"
   // (returns a signing link); the user's signature in the browser files it.
   | 'submit_vat_declaration'