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/git-mount-url-validation/.pi-map.index.md

@@ -0,0 +1,19 @@
+# openspec/changes/git-mount-url-validation (index)
+dir: openspec/changes/git-mount-url-validation
+
+## role
+Defines the specification and completion criteria for a high-priority feature that validates Git mount URLs.
+## parent
+index: openspec/changes/.pi-map.index.md
+map: openspec/changes/.pi-map.md
+## children
+-
+## files
+- .openspec.yaml
+## links
+index: openspec/changes/git-mount-url-validation/.pi-map.index.md
+map: openspec/changes/git-mount-url-validation/.pi-map.md
+## workflows
+-
+## dirty
+-