feat(month): confirm expected charges in one click

The repeated act, so it is a row and a button rather than a dialog — entry
speed is a product principle and a modal per bill would defeat it. The amount
is editable inline because paying a different figure is common; anything more
unusual is edited afterwards like any other purchase.

Confirmation is offered on a pending occurrence whose date has not arrived yet,
deliberately. A bill anchored to its last charge can charge EARLY, and
confirming the pending slot with the real date is how the series rebases.

The overdue count is not decoration. An occurrence nobody ever confirms holds
the projected balance down forever, which is the honest reading of an
unreconciled commitment but is invisible without it.

Returns null when nothing is expected, so a dataset with no recurring costs
sees no change to the month view at all.

src/ui/components/ExpectedBand.tsx

@@ -0,0 +1,125 @@
+import { useMemo, useState } from "react";
+import { Button } from "@/components/ui/button";
+import { Input } from "@/components/ui/input";
+import { useDataset } from "../hooks/useDataset.ts";
+import { useMutate } from "../hooks/useMutate.ts";
+import { confirmOccurrence } from "../../store/actions.ts";
+import { occurrencesByMonth } from "../../domain/occurrences.ts";
+import { compareMonths } from "../../domain/months.ts";
+import { parseMoneyInput } from "../moneyInput.ts";
+import { Section } from "./Section.tsx";
+import type { MonthId } from "../../domain/types.ts";
+
+/**
+ * The month's expected charges, and the one click that turns each into a real
+ * purchase.
+ *
+ * Confirmation is offered on any unconfirmed occurrence in this month,
+ * INCLUDING one whose date has not arrived yet. That is not an oversight: a
+ * bill anchored to its last charge can charge early — a phone plan whose data
+ * cap is hit on the 12th when the slot sat on the 30th — and confirming the
+ * pending slot with the real date is exactly how the series rebases.
+ */
+export function ExpectedBand({ monthId }: { monthId: MonthId }) {
+  const dataset = useDataset();
+  const { mutate } = useMutate();
+  const [amounts, setAmounts] = useState<Record<string, string>>({});
+
+  const { pending, overdue } = useMemo(() => {
+    const byMonth = occurrencesByMonth(dataset, monthId);
+    const thisMonth = (byMonth.get(monthId) ?? []).filter((o) => !o.confirmedBy);
+
+    // Everything unconfirmed in an EARLIER month. An occurrence nobody ever
+    // confirms holds the projected balance down forever, which is the honest
+    // reading of an unreconciled commitment — but it is silent unless counted.
+    let earlier = 0;
+    for (const [month, occurrences] of byMonth) {
+      if (compareMonths(month, monthId) >= 0) continue;
+      earlier += occurrences.filter((o) => !o.confirmedBy).length;
+    }
+
+    return { pending: thisMonth, overdue: earlier };
+  }, [dataset, monthId]);
+
+  if (pending.length === 0 && overdue === 0) return null;
+
+  const nameOf = (recurringId: string) =>
+    dataset.recurring.find((c) => c.id === recurringId)?.name ?? "Unknown";
+
+  return (
+    <Section
+      title="Expected"
+      hint="Committed but not yet spent. These do not touch a post's balance until you confirm one, which records it as an ordinary purchase you can edit or delete afterwards."
+    >
+      {pending.length > 0 && (
+        <ul className="divide-y divide-budget-rule">
+          {pending.map((occurrence) => {
+            const key = `${occurrence.recurringId}:${occurrence.date}`;
+            const typed = amounts[key];
+            return (
+              <li
+                key={key}
+                className="flex flex-wrap items-center justify-between gap-x-4 gap-y-2 py-2.5"
+              >
+                <div className="min-w-0">
+                  <div className="truncate text-sm">{nameOf(occurrence.recurringId)}</div>
+                  <div className="text-xs text-budget-ink-muted">{occurrence.date}</div>
+                </div>
+                <div className="flex items-center gap-2">
+                  <Input
+                    className="h-8 w-28"
+                    // text, not number: a number input discards the "$" before
+                    // parseMoneyInput can read it.
+                    type="text"
+                    aria-label={`Amount for ${nameOf(occurrence.recurringId)} on ${occurrence.date}`}
+                    value={typed ?? String(occurrence.amount.amount)}
+                    onChange={(event) => {
+                      const next = event.target.value;
+                      setAmounts((current) => ({ ...current, [key]: next }));
+                    }}
+                  />
+                  <span className="text-xs text-budget-ink-muted">
+                    {occurrence.amount.currency}
+                  </span>
+                  <Button
+                    size="sm"
+                    variant="outline"
+                    onClick={() => {
+                      // Captured before mutate, per AGENTS.md: mutate defers
+                      // behind the write queue and React resets the input
+                      // first, so reading in the callback commits stale text.
+                      const parsed =
+                        typed === undefined
+                          ? null
+                          : parseMoneyInput(typed, dataset.currencies, occurrence.amount.currency);
+                      mutate((draft) =>
+                        confirmOccurrence(draft, occurrence.recurringId, occurrence.date, {
+                          amount: parsed ?? undefined,
+                        }),
+                      );
+                      setAmounts((current) => {
+                        const next = { ...current };
+                        delete next[key];
+                        return next;
+                      });
+                    }}
+                  >
+                    Confirm
+                  </Button>
+                </div>
+              </li>
+            );
+          })}
+        </ul>
+      )}
+
+      {overdue > 0 && (
+        <p className="mt-3 text-xs leading-relaxed text-budget-ink-muted">
+          {overdue} earlier {overdue === 1 ? "occurrence has" : "occurrences have"} never
+          been confirmed. Until {overdue === 1 ? "it is" : "they are"}, the projected
+          balance stays lower than the real one by that amount.
+        </p>
+      )}
+    </Section>
+  );
+}

src/ui/routes/MonthRoute.tsx

@@ -15,6 +15,7 @@ import { sliceAmountForMonth } from "../../domain/charges.ts";
 import { useMoneyFormat } from "../hooks/useMoneyFormat.ts";
 import { PostTable, PostTableLegend } from "../components/PostTable.tsx";
 import { PurchaseDialog } from "../components/PurchaseDialog.tsx";
+import { ExpectedBand } from "../components/ExpectedBand.tsx";
 import { Meter } from "../components/Meter.tsx";
 import { Section, Stat } from "../components/Section.tsx";
 import { allocatedPercentOfIncome, allocationMeterSegments } from "../meterSegments.ts";
@@ -124,6 +125,8 @@ export function MonthRoute() {
         </div>
       </Section>
 
+      <ExpectedBand monthId={monthId} />
+
       <Section
         title="Posts"
         hint={<PostTableLegend baseCurrency={base} />}