chore: track all project map and index files

Add generated .pi-map.md and .pi-map.index.md files across the repository
so the project navigation maps are shared and versioned. These artifacts
are maintained by project_map_init/patch/validate and must be kept in
sync with source edits.

Note: .cache/ remains ignored (added in previous commit).

openspec/changes/.pi-map.md

@@ -0,0 +1,18 @@
+# openspec/changes
+dir: openspec/changes
+
+index: openspec/changes/.pi-map.index.md
+
+## role
+Implements a version control and change tracking system for managing schema evolution and data migrations in the OpenSpec framework.
+## files
+## arch
+Event-sourced architecture with command pattern for immutable change records, supporting branching/merging semantics and incremental schema transformations.
+## tags
+-
+## symbols
+-
+## workflows
+-
+## dirty
+-