chore: archive final 4 completed OpenSpec changes

Move the following completed changes from openspec/changes/ to
openspec/changes/archive/2026-06-12-completed-changes-archive/:
- multi-session-terminal-ux
- reorganize-long-files
- working-copies
- workspace-first-ui

Update parent and archive .pi-map*.md indexes to reflect the move and
remove the transient active-changes-archive grouping.

openspec/changes/ now contains only the archive/ directory.

openspec/changes/.pi-map.md

@@ -1,13 +1,27 @@
-# openspec/changes
-dir: openspec/changes
+# .
+dir: .
 
-index: openspec/changes/.pi-map.index.md
+index: ./.pi-map.index.md
+
+## Project Map Protocol
+
+1. Read this protocol and the root `.pi-map.index.md` first.
+2. Use `index:` / `map:` references to open relevant directory indexes and maps.
+3. Load indexes before rich maps during task-start navigation.
+4. Read the local rich map and actual source before editing.
+5. Treat non-empty `## dirty` sections in either artifact as stale.
+6. If source and generated artifacts disagree, trust source.
+7. If map and index disagree, trust neither blindly; verify from source and regenerate the pair.
+8. After editing source, run `project_map_patch` for each changed file.
+9. Before broad architectural claims or final handoff, run `project_map_validate` when freshness matters.
+
+Trust boundary: index routes, map orients, source decides.
 
 ## role
-Manages and tracks specification changes, versioning, and changelog generation for the OpenAPI specification.
+This is an empty directory with no files to analyze.
 ## files
 ## arch
-Event-sourced or diff-based architecture with structured change records, likely supporting incremental versioning and audit trails for specification evolution.
+N/A - no code or architecture present
 ## tags
 -
 ## symbols