Use sharp/angular tops for timeline event spikes

Remove the rounded-t Tailwind class from timeline bars so spike peaks
render as sharp, flat-topped rectangles instead of rounded corners,
making bucket boundaries clearer to read. Verified in the browser in
both light and dark theme.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XFUNZwCvz3kcod3352ZR2o

tickets/005-sharp-angular-timeline-spikes.md

@@ -1,7 +0,0 @@
-# Use sharp/angular tops for timeline event spikes
-
-The event spikes in the timeline should not have rounded tops. They should be sharp angular, for clearer reading.
-
-## Acceptance criteria
-- Timeline event spikes render with sharp, angular peaks instead of rounded/curved tops.
-- Change is visually verified in the browser (light and dark theme).

webapp/src/components/LogTimeline.tsx

@@ -165,7 +165,7 @@ export function LogTimeline({
           {buckets.map((b) => (
             <div
               key={b.start_ms}
-              className="absolute bottom-0 min-w-[2px] rounded-t bg-accent/70"
+              className="absolute bottom-0 min-w-[2px] bg-accent/70"
               style={{
                 left: `${((b.start_ms - domainStart) / domainSpan) * 100}%`,
                 width: `${(bucketMs / domainSpan) * 100}%`,