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/tests/.pi-map.index.md

@@ -0,0 +1,19 @@
+# archive/tests (index)
+dir: archive/tests
+
+## role
+Legacy or archived test directory currently containing only a placeholder file with no active test code.
+## parent
+index: archive/.pi-map.index.md
+map: archive/.pi-map.md
+## children
+-
+## files
+- .gitkeep
+## links
+index: archive/tests/.pi-map.index.md
+map: archive/tests/.pi-map.md
+## workflows
+-
+## dirty
+-

archive/tests/.pi-map.md

@@ -0,0 +1,19 @@
+# archive/tests
+dir: archive/tests
+
+index: archive/tests/.pi-map.index.md
+
+## role
+Legacy or archived test directory currently containing only a placeholder file with no active test code.
+## files
+- .gitkeep | Swaps the position of two tmux panes within a window or between windows | dep: tmux, sh
+## arch
+Empty placeholder structure using a `.gitkeep` file to preserve the directory in version control for potential future use.
+## tags
+tmux, swaps, position, two, panes, within, window, windows
+## symbols
+-
+## workflows
+-
+## dirty
+-