chore: track .pi-map.md and .pi-map.index.md artifacts

Remove the map files from .gitignore so they are committed as project
navigation artifacts, and also unignore them in the sample fixture.
Regenerate all maps so the committed versions reflect the current source.

openspec/changes/archive/.pi-map.md

@@ -0,0 +1,18 @@
+# openspec/changes/archive
+dir: openspec/changes/archive
+
+index: openspec/changes/archive/.pi-map.index.md
+
+## role
+Provides persistent storage and retrieval of historical change records in an archived format for audit trails and long-term data retention.
+## files
+## arch
+Simple archive storage pattern using file-based serialization with read/write operations for immutable change log records, likely with date-based or sequential naming conventions.
+## tags
+-
+## symbols
+-
+## workflows
+-
+## dirty
+-