chore: archive observability-service-registry, track pi-map artifacts

- Archive the completed observability-service-registry SDD change into
  openspec/changes/archive/ (delivered across 5 slices; only
  jellyfin-service-registry remains active).
- Stop ignoring .pi-map.md / .pi-map.index.md so the navigation maps are
  versioned alongside the code, and add the regenerated map pairs repo-wide.

.opencode/skills/openspec-archive-change/.pi-map.index.md

@@ -0,0 +1,19 @@
+# .opencode/skills/openspec-archive-change (index)
+dir: .opencode/skills/openspec-archive-change
+
+## role
+Provides a structured skill definition for archiving completed changes in the openspec experimental workflow with validation and user confirmation steps.
+## parent
+index: .opencode/skills/.pi-map.index.md
+map: .opencode/skills/.pi-map.md
+## children
+-
+## files
+- SKILL.md
+## links
+index: .opencode/skills/openspec-archive-change/.pi-map.index.md
+map: .opencode/skills/openspec-archive-change/.pi-map.md
+## workflows
+-
+## dirty
+-

.opencode/skills/openspec-archive-change/.pi-map.md

@@ -0,0 +1,19 @@
+# .opencode/skills/openspec-archive-change
+dir: .opencode/skills/openspec-archive-change
+
+index: .opencode/skills/openspec-archive-change/.pi-map.index.md
+
+## role
+Provides a structured skill definition for archiving completed changes in the openspec experimental workflow with validation and user confirmation steps.
+## files
+- SKILL.md | Defines a skill for archiving a completed change in the openspec experimental workflow, including validation, sync assessment, and user confirmation steps. | dep: openspec CLI, AskUserQuestion tool, Task tool (subagent_type: general-purpose), openspec-sync-specs skill
+## arch
+Single-document declarative skill specification following a procedural checklist pattern (validate, assess sync, confirm) designed for an AI agent to execute.
+## tags
+skill, openspec, sync, defines, archiving, completed, change, experimental
+## symbols
+-
+## workflows
+-
+## dirty
+-