fix: remove duplicate job loading on chart zoom (#8121)

- Remove explicit loadJobs(true) calls from onZoom handlers in RunChart
  and ConcurrentJobsChart — setting _timeframe.val already triggers the
  effect which calls onParamChanges
- Fix debounce by hoisting promise ref outside effect closure so cleanup
  can properly cancel in-flight requests

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/lib/components/RunsPage.svelte

@@ -776,9 +776,8 @@
 					maxTimeSet={manualTimeframe?.maxTs}
 					maxIsNow={manualTimeframe?.maxTs == undefined}
 					jobs={completedJobs}
-					onZoom={async (zoom) => {
+					onZoom={(zoom) => {
 						_timeframe.val = buildManualTimeframe(zoom.min.toISOString(), zoom.max.toISOString())
-						jobsLoader?.loadJobs(true)
 					}}
 					onPointClicked={(ids) => {
 						runsTable?.scrollToRun(ids)
@@ -790,9 +789,8 @@
 					maxTimeSet={manualTimeframe?.maxTs}
 					maxIsNow={manualTimeframe?.maxTs == undefined}
 					{extendedJobs}
-					onZoom={async (zoom) => {
+					onZoom={(zoom) => {
 						_timeframe.val = buildManualTimeframe(zoom.min.toISOString(), zoom.max.toISOString())
-						jobsLoader?.loadJobs(true)
 					}}
 				/>
 			{/if}

frontend/src/lib/components/runs/useJobsLoader.svelte.ts

@@ -110,6 +110,7 @@ export function useJobsLoader(args: () => UseJobLoaderArgs) {
 	let intervalId: ReturnType<typeof setInterval> | undefined = $state()
 	let sync = true
 	let paramChangeTimeout: ReturnType<typeof setTimeout> | undefined
+	let paramChangePromise: CancelablePromise<void> | undefined
 
 	function onParamChanges() {
 		resetJobs()
@@ -545,14 +546,14 @@ export function useJobsLoader(args: () => UseJobLoaderArgs) {
 		perPage
 		showSchedules
 		showFutureJobs
-		let p: CancelablePromise<void> | undefined
 		clearTimeout(paramChangeTimeout)
+		paramChangePromise?.cancel()
 		paramChangeTimeout = setTimeout(() => {
-			p = untrack(() => onParamChanges())
+			paramChangePromise = untrack(() => onParamChanges())
 		}, 0)
 		return () => {
 			clearTimeout(paramChangeTimeout)
-			p?.cancel()
+			paramChangePromise?.cancel()
 		}
 	})
 	$effect(() => {