chore: archive observability-service-registry, track pi-map artifacts

- Archive the completed observability-service-registry SDD change into
  openspec/changes/archive/ (delivered across 5 slices; only
  jellyfin-service-registry remains active).
- Stop ignoring .pi-map.md / .pi-map.index.md so the navigation maps are
  versioned alongside the code, and add the regenerated map pairs repo-wide.

frontend/src/test/.pi-map.index.md

@@ -0,0 +1,20 @@
+# frontend/src/test (index)
+dir: frontend/src/test
+
+## role
+Provides test infrastructure configuration for the frontend's Vitest testing environment.
+## parent
+index: frontend/src/.pi-map.index.md
+map: frontend/src/.pi-map.md
+## children
+-
+## files
+- setup.ts
+## links
+index: frontend/src/test/.pi-map.index.md
+map: frontend/src/test/.pi-map.md
+## workflows
+- change test behavior
+  read: setup.ts
+## dirty
+-

frontend/src/test/.pi-map.md

@@ -0,0 +1,23 @@
+# frontend/src/test
+dir: frontend/src/test
+
+index: frontend/src/test/.pi-map.index.md
+
+## role
+Provides test infrastructure configuration for the frontend's Vitest testing environment.
+## files
+- setup.ts | Configures Vitest global test environment by registering jest-dom matchers and polyfilling missing jsdom APIs for Radix/shadcn UI component testing. | exp: class:ResizeObserverStub, method:observe(), method:unobserve(), method:disconnect() | dep: @testing-library/jest-dom/vitest, vitest, jsdom
+## arch
+Setup module pattern that extends Vitest's global matchers with jest-dom and polyfills jsdom gaps for UI component compatibility.
+## tags
+vitest, jest, dom, jsdom, resize, observer, stub, observe
+## symbols
+- ResizeObserverStub
+- observe
+- unobserve
+- disconnect
+## workflows
+- change test behavior
+  read: setup.ts
+## dirty
+-