fix: comprehensive code quality, theming, and test coverage improvements

- Fix ExemptionManager apiVersion bug (apps/batch resources used wrong API path)
- Replace resource: any with proper KubeResource interface (strict TypeScript)
- Replace all var(--mui-palette-*) CSS variables with useTheme() + theme.palette.*
- Replace custom drawer with MUI Drawer component (proper a11y and theming)
- Replace alert() calls with StatusLabel-based inline feedback
- Add PolarisErrorBoundary wrapping all registered plugin components
- Export getPolarisApiPath/isFullUrl from polaris.ts, deduplicate in PolarisSettings
- Fix PolarisDataContext test mock missing triggerRefresh
- Fix DashboardView test SimpleTable mock using any
- Remove dead NamespaceDetailView (replaced by drawer), unused MockPolarisProvider,
  unused getSeverityColor export
- Add tests for InlineAuditSection, AppBarScoreBadge, topIssues, checkMapping (32 new)
- Update CLAUDE.md, CHANGELOG.md, README.md for v0.6.0

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

src/components/AppBarScoreBadge.tsx

@@ -1,3 +1,4 @@
+import { useTheme } from '@mui/material/styles';
 import React from 'react';
 import { useHistory } from 'react-router-dom';
 import { computeScore, countResults } from '../api/polaris';
@@ -8,6 +9,7 @@ import { usePolarisDataContext } from '../api/PolarisDataContext';
  * Clicking navigates to the overview dashboard
  */
 export default function AppBarScoreBadge() {
+  const theme = useTheme();
   const { data, loading } = usePolarisDataContext();
   const history = useHistory();
 
@@ -18,11 +20,17 @@ export default function AppBarScoreBadge() {
   const counts = countResults(data);
   const score = computeScore(counts);
 
-  // Color based on score
-  const getColor = (score: number): string => {
-    if (score >= 80) return '#4caf50'; // green
-    if (score >= 50) return '#ff9800'; // orange
-    return '#f44336'; // red
+  // Color based on score using theme palette
+  const getColor = (s: number): string => {
+    if (s >= 80) return theme.palette.success.main;
+    if (s >= 50) return theme.palette.warning.main;
+    return theme.palette.error.main;
+  };
+
+  const getContrastColor = (s: number): string => {
+    if (s >= 80) return theme.palette.success.contrastText;
+    if (s >= 50) return theme.palette.warning.contrastText;
+    return theme.palette.error.contrastText;
   };
 
   const handleClick = () => {
@@ -39,7 +47,7 @@ export default function AppBarScoreBadge() {
         borderRadius: '16px',
         border: 'none',
         backgroundColor: getColor(score),
-        color: 'white',
+        color: getContrastColor(score),
         fontSize: '13px',
         fontWeight: 500,
         display: 'inline-flex',
@@ -48,7 +56,6 @@ export default function AppBarScoreBadge() {
       }}
       aria-label={`Polaris cluster score: ${score}%`}
     >
-      <span>🛡️</span>
       <span>Polaris: {score}%</span>
     </button>
   );