chore: move source to repo root and standardize config

Phase 1 — Structural overhaul:
- Move all source from headlamp-sealed-secrets/ subdirectory to repo root
- Delete 23 AI-generated docs, 8 pre-built tarballs, release snapshots dir
- Remove all working-directory refs from CI/release workflows
- Update install-plugin.sh and typedoc.json paths

Phase 2 — Config standardization:
- Create .eslintrc.js and .prettierrc.js (standard Headlamp configs)
- Remove inline eslintConfig/prettier from package.json (drop jsx-a11y, prettier extends)
- Rewrite tsconfig.json (package name extend, add compilerOptions.types)
- Create vitest.config.mts and vitest.setup.ts (standard from polaris)
- Replace headlamp-plugin CLI scripts with direct tool invocation
- Rewrite .gitignore with standard baseline

Phase 3 — MCP & Claude settings:
- Create .mcp.json with github/kubernetes/flux/playwright servers
- Create .claude/settings.local.json
- Remove 7 specialized agents, keep 3 meta-orchestration agents

Phase 4 — Documentation:
- Rewrite CLAUDE.md (remove subdirectory refs, standard format)
- Add ArtifactHub badge, Architecture section, standardized install methods to README.md
- Create CONTRIBUTING.md and SECURITY.md
- Fix pre-existing test bugs in validators.test.ts (isValidNamespace returns boolean,
  not ValidationResult; error message string mismatches)

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

vitest.setup.ts

@@ -0,0 +1,43 @@
+import '@testing-library/jest-dom';
+
+// Node 22+ ships a minimal built-in `localStorage` global (property-bag only,
+// no getItem/setItem/removeItem/clear) that shadows jsdom's Web Storage
+// implementation. Provide a spec-compliant shim so code under test works.
+if (typeof localStorage !== 'undefined' && typeof localStorage.getItem !== 'function') {
+  const store = new Map<string, string>();
+
+  const storage = {
+    getItem(key: string): string | null {
+      return store.get(key) ?? null;
+    },
+    setItem(key: string, value: string): void {
+      store.set(key, String(value));
+    },
+    removeItem(key: string): void {
+      store.delete(key);
+    },
+    clear(): void {
+      store.clear();
+    },
+    get length(): number {
+      return store.size;
+    },
+    key(index: number): string | null {
+      return [...store.keys()][index] ?? null;
+    },
+  };
+
+  Object.defineProperty(globalThis, 'localStorage', {
+    value: storage,
+    writable: true,
+    configurable: true,
+  });
+
+  if (typeof window !== 'undefined') {
+    Object.defineProperty(window, 'localStorage', {
+      value: storage,
+      writable: true,
+      configurable: true,
+    });
+  }
+}