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/archive/2026-05-22-session-management-fixes/specs/.pi-map.md

@@ -0,0 +1,18 @@
+# openspec/changes/archive/2026-05-22-session-management-fixes/specs
+dir: openspec/changes/archive/2026-05-22-session-management-fixes/specs
+
+index: openspec/changes/archive/2026-05-22-session-management-fixes/specs/.pi-map.index.md
+
+## role
+Contains archived specification documents for session management fixes from a May 2026 release, serving as historical documentation for past API design decisions.
+## files
+## arch
+Flat directory structure storing dated specification snapshots with no active code or architectural patterns—purely document archival using filesystem-based versioning.
+## tags
+-
+## symbols
+-
+## workflows
+-
+## dirty
+-