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/2026-05-19-documentation-overhaul/.pi-map.md

@@ -0,0 +1,22 @@
+# openspec/changes/archive/2026-05-19-documentation-overhaul
+dir: openspec/changes/archive/2026-05-19-documentation-overhaul
+
+index: openspec/changes/archive/2026-05-19-documentation-overhaul/.pi-map.index.md
+
+## role
+Contains archived planning documents for a 2026 documentation overhaul initiative, including configuration, design, proposal, and task tracking artifacts.
+## files
+- .openspec.yaml | Defines an OpenSpec configuration file with schema type and creation date metadata
+- design.md | Defines the structure, templates, and process for overhauling a project's documentation system
+- proposal.md | Proposes a comprehensive documentation overhaul for a software project to address gaps in README, feature docs, API docs, deployment guides, and architecture documentation.
+- tasks.md | Task tracking document for a comprehensive documentation overhaul project spanning README rewrite, documentation structure creation, feature/API/architecture documentation, deployment/development guides, and finalization
+## arch
+Document-driven project planning pattern using structured markdown specifications with YAML metadata, following a progression from proposal → design → tasks workflow with explicit schema versioning.
+## tags
+documentation, project, defines, creation, .openspec, structure, design, comprehensive
+## symbols
+-
+## workflows
+-
+## dirty
+-