refactor: plan timeframes use a per-day-of-week picker (like the V2 tariff)

The timeframes model was a coarse weekday/weekend split, which couldn't express
"open Saturdays" or different rules on a specific day — and it didn't match the
V2 tariff, which already has a proper per-day-of-week picker (Hën–Die).

Replace PlanTimeframes { weekday, weekend } with { days[], fromMin, toMin }: the
allowed window applies only on the selected days (0=Sun..6=Sat; empty = every
day); on unselected days the subscriber parks free. A "night plan, free
weekends" is just days [Mon..Fri] with a 20:00→08:00 window — the exact case
from before, now expressible alongside any other day combination.

outOfWindowGap reworked to the days model (per-day membership test instead of
the weekend helper); the plans editor reuses the tariff composer's Mon-first
checkbox row and the shared tariff.dow0..6 labels. No production plans carry
timeframes yet (feature shipped today), so the shape changed directly with no
migration. Unit tests updated + extended (Saturday-only, every-day, weekday
night); 81 shared tests pass. Build+lint 12/12.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

packages/shared/src/subscription-window.test.ts

@@ -4,15 +4,17 @@ import { outOfWindowGap, type PlanTimeframes } from "./index.js";
 // The "tariff bridge" gap for a subscriber scan outside their allowed window. UTC tz
 // keeps the wall-clock arithmetic obvious in the tests. See wiki/entities/subscription.md.
 
-// Night plan: weekday allowed 20:00→08:00 (wraps midnight); weekend all-day.
+// Night plan: window 20:00→08:00 (wraps midnight) on weekdays (Mon..Fri). Days not in the
+// set (Sat/Sun) are unrestricted — no charge.
 const night: PlanTimeframes = {
-  weekday: { fromMin: 20 * 60, toMin: 8 * 60 }, // 1200 → 480
-  weekend: { allDay: true },
+  days: [1, 2, 3, 4, 5], // Mon..Fri
+  fromMin: 20 * 60,
+  toMin: 8 * 60, // 1200 → 480
   graceMin: 0,
   tz: "UTC",
 };
 
-// A weekday + a weekend (2026-06-22 is a Monday; 2026-06-20 is a Saturday).
+// 2026-06-22 is a Monday; 2026-06-20 is a Saturday.
 const monday = (hhmm: string) => `2026-06-22T${hhmm}:00.000Z`;
 const saturday = (hhmm: string) => `2026-06-20T${hhmm}:00.000Z`;
 
@@ -49,11 +51,20 @@ describe("outOfWindowGap — exit edge (late departure)", () => {
   });
 });
 
-describe("outOfWindowGap — weekend all-day", () => {
-  it("any Saturday scan is free (entry + exit)", () => {
+describe("outOfWindowGap — days the window doesn't apply", () => {
+  it("a Saturday scan is free (window only Mon..Fri)", () => {
     expect(outOfWindowGap(night, "UTC", saturday("09:00"), "entry")).toBeNull();
     expect(outOfWindowGap(night, "UTC", saturday("23:30"), "exit")).toBeNull();
   });
+  it("a window with no days (every day) DOES apply on Saturday", () => {
+    const everyDay: PlanTimeframes = { fromMin: 1200, toMin: 480, tz: "UTC" };
+    expect(outOfWindowGap(everyDay, "UTC", saturday("09:00"), "entry")).not.toBeNull();
+  });
+  it("an arbitrary day set (e.g. only Saturday) applies just then", () => {
+    const satOnly: PlanTimeframes = { days: [6], fromMin: 1200, toMin: 480, tz: "UTC" };
+    expect(outOfWindowGap(satOnly, "UTC", saturday("09:00"), "entry")).not.toBeNull();
+    expect(outOfWindowGap(satOnly, "UTC", monday("09:00"), "entry")).toBeNull();
+  });
 });
 
 describe("outOfWindowGap — grace tolerance", () => {
@@ -74,9 +85,4 @@ describe("outOfWindowGap — unrestricted", () => {
   it("null timeframes → never a charge", () => {
     expect(outOfWindowGap(null, "UTC", monday("09:00"), "entry")).toBeNull();
   });
-  it("a day-type with no window → no charge", () => {
-    const weekdayOnly: PlanTimeframes = { weekday: { fromMin: 1200, toMin: 480 }, tz: "UTC" };
-    // weekend absent ⇒ unrestricted on Saturday.
-    expect(outOfWindowGap(weekdayOnly, "UTC", saturday("09:00"), "entry")).toBeNull();
-  });
 });