ref(dynamic-sampling): Add aria-label to project rate input

Add an accessible label to each project's sample rate input so screen
readers can identify which project the input belongs to. Update the
test helper to query by this label instead of relying on positional
spinbutton indexing.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: priscilawebdev

static/app/views/settings/dynamicSampling/projectSampling.spec.tsx

@@ -58,17 +58,10 @@ describe('ProjectSampling', () => {
     });
   });
 
-  function getProjectRateInput() {
-    // The first spinbutton is the org rate, the second is the project rate
-    const inputs = screen.getAllByRole('spinbutton');
-    return inputs[inputs.length - 1]!;
-  }
-
   async function waitForProjectRateInput() {
-    // Wait for the project table to render — the ProjectBadge component
-    // renders a link with this accessible name
-    await screen.findByRole('link', {name: 'View Project Details'});
-    return getProjectRateInput();
+    return screen.findByRole('spinbutton', {
+      name: 'Sample rate for project-slug',
+    });
   }
 
   it('renders project rate inputs with initial values', async () => {

static/app/views/settings/dynamicSampling/projectsTable.tsx

@@ -394,6 +394,7 @@ const TableRow = memo(function TableRow({
               onChange={handleChange}
               size="sm"
               value={sampleRate}
+              aria-label={t('Sample rate for %s', project.slug)}
             />
           </Tooltip>
         </FirstCellLine>