fix: show active filters in empty state instead of clearing on page switch

Reverts automatic filter clearing on page switch so filters stay
sticky. When filters cause zero results, the empty state now shows
which filters are active and provides a 'Clear all filters' button.

Author: austenstone

src/components/ReportPageLayout.tsx

@@ -570,8 +570,15 @@ export function ReportPageLayout({ schema, allowedReportTypes, metricOptions }:
                 No matching usage rows
               </Heading>
               <Text as="p" className={styles.surfaceDescription}>
-                Try a different search term or clear the current period filter.
+                {Object.keys(filters).length > 0
+                  ? `Active filters (${Object.entries(filters).map(([k, v]) => `${k}: ${v.join(', ')}`).join('; ')}) may not apply to this report.`
+                  : 'Try a different search term or clear the current period filter.'}
               </Text>
+              {Object.keys(filters).length > 0 && (
+                <Button variant="default" size="small" onClick={clearAllToolbarFilters} sx={{ mt: 2 }}>
+                  Clear all filters
+                </Button>
+              )}
             </div>
           )}