feat(race-day): start heats with an EFRA/IFMAR count-down and flying start

Race Day Start now runs a count-down (Go, 30 s - 5 min, default per
event) with calls every minute, 30 s and 10 s, grid call and 9..3
count for grid starts, hold/resume/+1 min/to 30 s/to 10 s/Go now, and
starts the heat by itself when it runs out. The transponder check runs
during the count-down, replacing the separate warm-up.

Adds a flying start mode (horn + clock is running, own clock per car)
as the qualifying default, and the latest personal clock start rules
from EFRA 9.3 / IFMAR 4.2.3 for flying and staggered starts.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/decoder_runtime.test.js

@@ -12,7 +12,7 @@ function createHarness(options = {}) {
     mode: "race",
     type: options.sessionType || "team_race",
     status: "running",
-    startMode: "mass",
+    startMode: options.startMode || "mass",
     startedAt: 1_000,
   };
   const state = {
@@ -36,7 +36,7 @@ function createHarness(options = {}) {
     t: (key) => key,
     getActiveSession: () => session,
     ensureSessionResult: (sessionId) => ensureSessionResult(sessionId, { state }),
-    normalizeStartMode: () => "mass",
+    normalizeStartMode: () => options.startMode || "mass",
     getSessionLapWindow: () => ({
       minLapMs: Number(options.minLapMs || 0),
       maxLapMs: options.maxLapMs == null ? Number.POSITIVE_INFINITY : Number(options.maxLapMs),
@@ -112,6 +112,30 @@ test("maximum lap time starts a statistics stint but still counts the race lap",
   assert.equal(result.passings[0].stintBoundary, true);
 });
 
+test("flying start: each car's clock starts at its own first crossing, a late car's at the latest 150 % of a lap (EFRA 9.3)", () => {
+  const harness = createHarness({ sessionType: "qualification", startMode: "flying" });
+  const byDriver = (driverId) => Object.values(harness.state.resultsBySession.session_1.competitors).find((entry) => entry.driverId === driverId);
+  harness.passing(4_000, "main", "123"); // Driver One's clock starts - not a lap
+  assert.equal(byDriver("driver_1").startTimestamp, 4_000);
+  assert.equal(byDriver("driver_1").laps, 0);
+  harness.passing(24_000, "main", "123"); // first lap anyone completes: 20 s -> latest start 1 000 + 30 000
+  assert.equal(byDriver("driver_1").laps, 1);
+  harness.passing(29_000, "main", "456"); // Driver Two just in time: own clock
+  assert.equal(byDriver("driver_2").startTimestamp, 29_000);
+  assert.equal(byDriver("driver_2").laps, 0);
+});
+
+test("flying start: a car first seen after the latest clock start gets that clock and its crossing counts as a lap", () => {
+  const harness = createHarness({ sessionType: "qualification", startMode: "flying" });
+  const byDriver = (driverId) => Object.values(harness.state.resultsBySession.session_1.competitors).find((entry) => entry.driverId === driverId);
+  harness.passing(4_000, "main", "123");
+  harness.passing(24_000, "main", "123"); // latest start = 31 000
+  harness.passing(45_000, "main", "456");
+  assert.equal(byDriver("driver_2").startTimestamp, 31_000);
+  assert.equal(byDriver("driver_2").laps, 1);
+  assert.equal(byDriver("driver_2").lastLapMs, 14_000);
+});
+
 test("pit entry and exit create one timed stop without adding laps", () => {
   const harness = createHarness();
   harness.passing(17_000, "main");