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).

.opencode/.pi-map.md

@@ -0,0 +1,18 @@
+# .opencode
+dir: .opencode
+
+index: .opencode/.pi-map.index.md
+
+## role
+Configuration directory for the OpenCode AI coding assistant tool
+## files
+## arch
+Tool-specific configuration storage using standard dot-directory convention with likely JSON/YAML config files and optional workspace state/logs
+## tags
+-
+## symbols
+-
+## workflows
+-
+## dirty
+-