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.

archive/.pi-map.md

@@ -0,0 +1,26 @@
+# archive
+dir: archive
+
+index: archive/.pi-map.index.md
+
+## role
+Archive of an earlier project structure for a Streamlit-based Jellyfin media library browser with SSH remote file inspection capabilities.
+## files
+- app.py | Provides a minimal Streamlit entrypoint that adds the src directory to Python's path and delegates to the actual application in media_library_viewer.app. | dep: sys, pathlib, media_library_viewer.app
+- pyproject.toml | Defines Python package metadata, dependencies, and tool configurations for a Streamlit-based Jellyfin media library browser with SSH remote file inspection. | dep: hatchling, streamlit, streamlit-aggrid, requests, paramiko, python-dotenv, pandas, ruff, pytest
+- requirements.txt | Installs the current package in editable/development mode using pip | dep: pip, setuptools
+## arch
+Thin entrypoint pattern using a bootstrap app.py that manipulates sys.path to delegate execution to a nested media_library_viewer package, managed via standard Python packaging (pyproject.toml).
+## tags
+streamlit, app, python, media, library, package, pyproject, pip
+## symbols
+-
+## workflows
+- change archive behavior
+  read: app.py, pyproject.toml, requirements.txt
+- change archive config
+  read: pyproject.toml
+- explore archive subdirectories
+  index: archive/src/.pi-map.index.md, archive/tests/.pi-map.index.md
+## dirty
+-