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).

apps/.pi-map.index.md

@@ -0,0 +1,23 @@
+# apps (index)
+dir: apps
+
+## role
+Contains the main application entry points and executable modules for the project.
+## parent
+index: ./.pi-map.index.md
+map: ./.pi-map.md
+## children
+- apps/api
+  index: apps/api/.pi-map.index.md
+  map: apps/api/.pi-map.md
+- apps/web
+  index: apps/web/.pi-map.index.md
+  map: apps/web/.pi-map.md
+## files
+## links
+index: apps/.pi-map.index.md
+map: apps/.pi-map.md
+## workflows
+-
+## dirty
+-