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-sessions-hub/.pi-map.md

@@ -0,0 +1,21 @@
+# openspec/changes/archive/2026-05-22-sessions-hub
+dir: openspec/changes/archive/2026-05-22-sessions-hub
+
+index: openspec/changes/archive/2026-05-22-sessions-hub/.pi-map.index.md
+
+## role
+Design and planning package for a centralized Sessions Hub feature that manages user workspace sessions across projects.
+## files
+- design.md | Design document for implementing a Sessions Hub feature with page layout, navigation, data flow, and API changes for managing user workspace sessions. | dep: Navigation, AppShell, SessionsPage, UserConfig, API endpoints (/users/me/sessions, /users/me/config), workspace, state management, polling
+- proposal.md | Proposes a centralized "Sessions Hub" feature for managing active tool instances across projects
+- tasks.md | Project task tracking document for implementing a Sessions Hub feature across backend and frontend | dep: UserConfig model, Alembic, Pydantic, AppShell, React Router, sessions context, workspace, npm
+## arch
+Specification-driven architecture using markdown-based design documents (design.md, proposal.md, tasks.md) to define requirements, API contracts, and implementation tasks before code development.
+## tags
+sessions, design, hub, feature, workspace, document, implementing, navigation
+## symbols
+-
+## workflows
+-
+## dirty
+-