fix: prevent IEEE 754 precision loss in nanosecond timestamp conversion

Multiplying epoch milliseconds by 1_000_000 as a Number before converting
to BigInt exceeds Number.MAX_SAFE_INTEGER (~9e15), causing ~256ns precision
errors in ~0.2% of cases (epoch-ms * 1e6 ≈ 1.7e18).

Fix: convert to BigInt first, then multiply.
- getNowInNanoseconds(): BigInt(ms) * BigInt(1_000_000)
- calculateDurationFromStart(): same pattern
- recordRunDebugLog() in index.server.ts: same
- runEngineHandlers.server.ts retry event startTime: same

convertDateToNanoseconds() already used the correct pattern — aligned
all callers to match it.

Fixes #3292

Author: selenaalpha77-sketch

apps/webapp/app/v3/eventRepository/common.server.ts

@@ -21,7 +21,7 @@ export function extractContextFromCarrier(carrier: Record<string, unknown>) {
 }
 
 export function getNowInNanoseconds(): bigint {
-  return BigInt(new Date().getTime() * 1_000_000);
+  return BigInt(new Date().getTime()) * BigInt(1_000_000);
 }
 
 export function getDateFromNanoseconds(nanoseconds: bigint): Date {
@@ -35,7 +35,7 @@ export function calculateDurationFromStart(
 ) {
   const $endtime = typeof endTime === "string" ? new Date(endTime) : endTime;
 
-  const duration = Number(BigInt($endtime.getTime() * 1_000_000) - startTime);
+  const duration = Number(BigInt($endtime.getTime()) * BigInt(1_000_000) - startTime);
 
   if (minimumDuration && duration < minimumDuration) {
     return minimumDuration;

apps/webapp/app/v3/eventRepository/index.server.ts

@@ -215,7 +215,7 @@ async function recordRunEvent(
         runId: foundRun.friendlyId,
         ...attributes,
       },
-      startTime: BigInt((startTime?.getTime() ?? Date.now()) * 1_000_000),
+      startTime: BigInt(startTime?.getTime() ?? Date.now()) * BigInt(1_000_000),
       ...optionsRest,
     });
 

apps/webapp/app/v3/runEngineHandlers.server.ts

@@ -429,7 +429,7 @@ export function registerRunEngineEventBusHandlers() {
       const eventRepository = resolveEventRepositoryForStore(run.taskEventStore);
 
       await eventRepository.recordEvent(retryMessage, {
-        startTime: BigInt(time.getTime() * 1000000),
+        startTime: BigInt(time.getTime()) * BigInt(1_000_000),
         taskSlug: run.taskIdentifier,
         environment,
         attributes: {