fix: remove profile.start_timestamp from mapping

Only consumed by the transaction-based processEvent profiling path,
not by span streaming. The fallback uses the span's own start_timestamp.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: chargome

packages/core/src/tracing/spans/scopeContextAttributes.ts

@@ -27,9 +27,6 @@ export function scopeContextsToSpanAttributes(contexts: Contexts): Record<string
     if (profile.profiler_id) {
       attrs['sentry.profiler_id'] = profile.profiler_id;
     }
-    if (profile.start_timestamp != null) {
-      attrs['profile.start_timestamp'] = profile.start_timestamp;
-    }
   }
 
   // CloudResourceContext keys are already in dot-notation (OTel resource conventions)

packages/core/test/lib/tracing/spans/captureSpan.test.ts

@@ -682,14 +682,6 @@ describe('scopeContextsToSpanAttributes', () => {
       });
     });
 
-    it('maps start_timestamp', () => {
-      const contexts: Contexts = { profile: { profile_id: 'abc', start_timestamp: 1234567890 } };
-      expect(scopeContextsToSpanAttributes(contexts)).toEqual({
-        'sentry.profile_id': 'abc',
-        'profile.start_timestamp': 1234567890,
-      });
-    });
-
     it('produces no attributes for empty profile context', () => {
       const contexts: Contexts = { profile: { profile_id: '' } };
       expect(scopeContextsToSpanAttributes(contexts)).toEqual({});