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/api/src/models/.pi-map.index.md

@@ -0,0 +1,37 @@
+# apps/api/src/models (index)
+dir: apps/api/src/models
+
+## role
+Provides the core database model layer with a centralized public API, defining SQLAlchemy base classes and reusable mixins for consistent schema patterns across the API application.
+## parent
+index: apps/api/src/.pi-map.index.md
+map: apps/api/src/.pi-map.md
+## children
+- apps/api/src/models/config
+  index: apps/api/src/models/config/.pi-map.index.md
+  map: apps/api/src/models/config/.pi-map.md
+- apps/api/src/models/project
+  index: apps/api/src/models/project/.pi-map.index.md
+  map: apps/api/src/models/project/.pi-map.md
+- apps/api/src/models/system
+  index: apps/api/src/models/system/.pi-map.index.md
+  map: apps/api/src/models/system/.pi-map.md
+- apps/api/src/models/tool
+  index: apps/api/src/models/tool/.pi-map.index.md
+  map: apps/api/src/models/tool/.pi-map.md
+- apps/api/src/models/user
+  index: apps/api/src/models/user/.pi-map.index.md
+  map: apps/api/src/models/user/.pi-map.md
+## files
+- __init__.py
+- base.py
+## links
+index: apps/api/src/models/.pi-map.index.md
+map: apps/api/src/models/.pi-map.md
+## workflows
+- change models behavior
+  read: __init__.py, base.py
+- explore models subdirectories
+  index: apps/api/src/models/config/.pi-map.index.md, apps/api/src/models/project/.pi-map.index.md, apps/api/src/models/system/.pi-map.index.md
+## dirty
+-