feat(design): the Copy rule — names, verbs, dates and units (E28 S3g)

The owner's picks (all the recommended options) become DESIGN.md's Copy
chapter and a sweep of both languages (742 values, no key drift):

- One name per feature: the rail's label, which may shorten it (Alerts
  -> Notifications, Fiókok -> Felhasználók, Download Center -> Downloads,
  Channel manager -> Channels); one "sync from YouTube" verb.
- Four verbs, four meanings (Delete / Remove / Dismiss / Discard, and
  their Hungarian pairs), checked against what each action does.
- Sentence case, the app's places capitalised; "…" on a command that
  asks first (a popover or form title got its own key without it);
  one-sentence messages without a stop or a tick, "Couldn't …"; curly
  quotes.
- Dates only from lib/format.ts, in the UI language: formatDateTime
  names the month and stops at the minute (it printed "9/27/2026,
  8:30:14 AM"), formatDateTimeSec for the log, the audit and the
  recorder; ui/RelativeTime pairs "3d ago" with the exact minute on
  hover. local/date-format refuses toLocale*String and Intl date
  formatters elsewhere.
- Units from Intl, short (formatUnit): runtimes, totals, the Scheduler
  countdown, the stats range, the player's tap skip. "2h 13m" was
  English in both languages.
- src/i18n/copyRule.test.ts holds the machine-readable part (quotes,
  "...", ticks, bare unit letters).

frontend/src/lib/format.test.ts

@@ -3,6 +3,7 @@ import {
   RELATIVE_UNITS,
   formatDate,
   formatDateTime,
+  formatDateTimeSec,
   formatNumber,
   formatRuntime,
   formatTotalHours,
@@ -161,7 +162,7 @@ describe("formatNumber", () => {
 
   it("carries the UI language into the channel total-hours label", () => {
     i18nStub.language = "hu";
-    expect(formatTotalHours(12345 * 3600)).toBe(`${new Intl.NumberFormat("hu").format(12345)} h`);
+    expect(formatTotalHours(12345 * 3600)).toBe(`${new Intl.NumberFormat("hu").format(12345)} ó`);
   });
 });
 
@@ -170,26 +171,32 @@ describe("formatRuntime", () => {
     [null, ""],
     [undefined, ""],
     [0, ""], // nothing to show — the call sites suppress their separator on the empty string
-    [1, "1s"],
-    [45, "45s"], // one Short: the regression case
-    [45.7, "45s"], // truncates, so the seconds tier cannot overstate either
-    [59, "59s"], // last second before the minute tier
-    [60, "1m"],
-    [90, "1m"], // floors, never rounds up — a total must not overstate
-    [90.9, "1m"],
-    [3599, "59m"],
-    [3600, "1h 0m"], // the zero minutes stay: "1h" alone reads as an approximation
-    [5025, "1h 23m"],
-    [360000, "100h 0m"], // a large aggregate keeps counting hours rather than rolling to days
+    [1, "1 sec"],
+    [45, "45 sec"], // one Short: the regression case
+    [45.7, "45 sec"], // truncates, so the seconds tier cannot overstate either
+    [59, "59 sec"], // last second before the minute tier
+    [60, "1 min"],
+    [90, "1 min"], // floors, never rounds up — a total must not overstate
+    [90.9, "1 min"],
+    [3599, "59 min"],
+    [3600, "1 hr 0 min"], // the zero minutes stay: "1 hr" alone reads as an approximation
+    [5025, "1 hr 23 min"],
+    [360000, "100 hr 0 min"], // a large aggregate keeps counting hours rather than rolling to days
   ];
 
   it.each(CASES)("formats %o as %o", (sec, expected) => {
     expect(formatRuntime(sec)).toBe(expected);
   });
 
+  it("speaks the UI language's units (DESIGN Copy: Intl short), not English letters", () => {
+    i18nStub.language = "hu";
+    expect(formatRuntime(5025)).toBe("1 ó 23 p");
+    i18nStub.language = "en";
+  });
+
   it("never reports a non-zero duration as zero", () => {
     for (let sec = 1; sec < 3600; sec++) {
-      expect(formatRuntime(sec), `${sec}s`).not.toBe("0m");
+      expect(formatRuntime(sec), `${sec}s`).not.toBe("0 min");
     }
   });
 });
@@ -212,12 +219,20 @@ describe("formatDateTime / formatDate", () => {
     const asEnglish = formatDateTime(iso);
     i18nStub.language = "hu";
     const asHungarian = formatDateTime(iso);
-    expect(asEnglish).toBe(new Date(iso).toLocaleString("en"));
-    expect(asHungarian).toBe(new Date(iso).toLocaleString("hu"));
     expect(asEnglish).not.toBe(asHungarian);
     expect(formatDate(iso, "en")).not.toBe(formatDate(iso, "hu"));
   });
 
+  it("names the month and stops at the minute; seconds only in the log form (DESIGN Copy)", () => {
+    process.env.TZ = "UTC";
+    const iso = "2026-09-17T08:30:14Z";
+    expect(formatDateTime(iso)).toBe("Sep 17, 2026, 08:30 AM");
+    expect(formatDateTimeSec(iso)).toBe("Sep 17, 2026, 08:30:14 AM");
+    i18nStub.language = "hu";
+    expect(formatDateTime(iso)).toBe("2026. szept. 17. 08:30");
+    expect(formatDate(iso, "hu")).toBe("2026. szept. 17.");
+  });
+
   it("shows a date-only value as that calendar day in every time zone", () => {
     process.env.TZ = "America/New_York";
     expect(formatDate("2026-09-17", "en")).toBe("Sep 17, 2026");