feat(orders): add order-anchored fuzzy search window

Adds quoteWindowForOrder (pure) to constrain the fuzzy-match candidate
scan to a date window anchored on the order's own created date, plus
the forward grace period for quotes raised a few days after the PO.
Also adds quoteToOrderAgeDays, used by a later task's age-gap
histogram, with test coverage the plan omitted (normal, inverted, and
unparseable-input cases).

src/lib/server/order-quote-match.test.ts

@@ -10,6 +10,10 @@ import {
   pairQuoteLines,
   LINE_PAIR_CONFIDENT,
   LINE_PAIR_POSSIBLE,
+  quoteWindowForOrder,
+  quoteToOrderAgeDays,
+  FUZZY_WINDOW_DAYS,
+  FUZZY_WINDOW_WIDEN_DAYS,
 } from "@/lib/server/order-quote-match";
 
 /**
@@ -484,3 +488,55 @@ describe("pairQuoteLines", () => {
     expect(new Set(quoteIdxs).size).toBe(quoteIdxs.length);
   });
 });
+
+describe("quoteWindowForOrder", () => {
+  const ORDER_DATE = "2026-08-29T10:00:00.000Z";
+
+  it("looks back the requested number of days from the ORDER date, not from now", () => {
+    const w = quoteWindowForOrder(ORDER_DATE, 90);
+    expect(w.from).toBe("2026-05-31T10:00:00.000Z");
+  });
+
+  it("extends forward by the grace period so a quote raised just after the PO still matches", () => {
+    const w = quoteWindowForOrder(ORDER_DATE, 90);
+    expect(w.to).toBe("2026-09-05T10:00:00.000Z");
+  });
+
+  it("widens correctly for the fallback pass", () => {
+    const w = quoteWindowForOrder(ORDER_DATE, FUZZY_WINDOW_WIDEN_DAYS);
+    expect(new Date(w.from).getTime()).toBeLessThan(
+      new Date(quoteWindowForOrder(ORDER_DATE, FUZZY_WINDOW_DAYS).from).getTime(),
+    );
+  });
+
+  it("throws on an unparseable order date rather than silently matching everything", () => {
+    expect(() => quoteWindowForOrder("not-a-date", 90)).toThrow(/unparseable/i);
+  });
+});
+
+describe("quoteToOrderAgeDays", () => {
+  it("returns a positive day count when the quote precedes the order (normal case)", () => {
+    // Quote created 2026-06-01, order created 2026-08-29 → quote first,
+    // order 89 days later.
+    const days = quoteToOrderAgeDays(
+      "2026-06-01T10:00:00.000Z",
+      "2026-08-29T10:00:00.000Z",
+    );
+    expect(days).toBe(89);
+  });
+
+  it("returns a negative day count when the quote is created after the order (inverted case)", () => {
+    // Quote created 5 days after the order.
+    const days = quoteToOrderAgeDays(
+      "2026-08-29T10:00:00.000Z",
+      "2026-08-24T10:00:00.000Z",
+    );
+    expect(days).toBe(-5);
+  });
+
+  it("returns 0 (not NaN) when either input is unparseable", () => {
+    expect(quoteToOrderAgeDays("not-a-date", "2026-08-29T10:00:00.000Z")).toBe(0);
+    expect(quoteToOrderAgeDays("2026-08-29T10:00:00.000Z", "not-a-date")).toBe(0);
+    expect(Number.isNaN(quoteToOrderAgeDays("garbage", "also-garbage"))).toBe(false);
+  });
+});

src/lib/server/order-quote-match.ts

@@ -431,3 +431,64 @@ export function pairQuoteLines(
     tier: p.jaccard >= LINE_PAIR_CONFIDENT ? "confident" : "possible",
   }));
 }
+
+/* ============================================================================
+ * Fuzzy search window
+ *
+ * The 200-candidate cap alone behaves inconsistently: for a high-volume
+ * company it reaches back weeks, for a quiet one it reaches back years.
+ * Anchoring on a date window normalises that and matches how the
+ * business works — a quote normally converts within about two months.
+ *
+ * The window is measured from the ORDER's own created date, never from
+ * `Date.now()`. A "last 90 days from today" filter would find zero
+ * candidates for every order in the backlog sweep.
+ *
+ * This applies ONLY to the fuzzy description+price path. The four
+ * exact-identifier lookups are never date limited — a PO citing
+ * Q-2024-0847 should resolve however old that quote is.
+ * ========================================================================== */
+
+export const FUZZY_WINDOW_DAYS = 90;
+export const FUZZY_WINDOW_WIDEN_DAYS = 365;
+/** Forward grace for a quote raised just after the PO landed. */
+export const FUZZY_WINDOW_GRACE_DAYS = 7;
+
+const DAY_MS = 24 * 60 * 60 * 1000;
+
+export interface QuoteWindow {
+  /** Inclusive lower bound, ISO 8601. */
+  from: string;
+  /** Inclusive upper bound, ISO 8601. */
+  to: string;
+}
+
+/** Build the candidate-quote date window for one order. */
+export function quoteWindowForOrder(
+  orderCreated: string,
+  days: number,
+): QuoteWindow {
+  const anchor = new Date(orderCreated);
+  if (Number.isNaN(anchor.getTime())) {
+    throw new Error(
+      `quoteWindowForOrder: unparseable order date ${JSON.stringify(orderCreated)}`,
+    );
+  }
+  return {
+    from: new Date(anchor.getTime() - days * DAY_MS).toISOString(),
+    to: new Date(anchor.getTime() + FUZZY_WINDOW_GRACE_DAYS * DAY_MS).toISOString(),
+  };
+}
+
+/** Whole days between a quote's creation and an order's creation.
+ *  Positive means the quote came first (the normal case). Used by the
+ *  sweep's age-gap histogram. */
+export function quoteToOrderAgeDays(
+  quoteCreated: string,
+  orderCreated: string,
+): number {
+  const q = new Date(quoteCreated).getTime();
+  const o = new Date(orderCreated).getTime();
+  if (Number.isNaN(q) || Number.isNaN(o)) return 0;
+  return Math.round((o - q) / DAY_MS);
+}