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.index.md

@@ -0,0 +1,23 @@
+# .opencode (index)
+dir: .opencode
+
+## role
+Configuration directory for the OpenCode AI coding assistant tool
+## parent
+index: ./.pi-map.index.md
+map: ./.pi-map.md
+## children
+- .opencode/commands
+  index: .opencode/commands/.pi-map.index.md
+  map: .opencode/commands/.pi-map.md
+- .opencode/skills
+  index: .opencode/skills/.pi-map.index.md
+  map: .opencode/skills/.pi-map.md
+## files
+## links
+index: .opencode/.pi-map.index.md
+map: .opencode/.pi-map.md
+## workflows
+-
+## dirty
+-