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).

.claude/skills/sift-backlog/.pi-map.index.md

@@ -0,0 +1,19 @@
+# .claude/skills/sift-backlog (index)
+dir: .claude/skills/sift-backlog
+
+## role
+Defines a workflow skill for triaging, organizing, and activating backlog tasks into actionable plans using a custom CLI tool.
+## parent
+index: .claude/skills/.pi-map.index.md
+map: .claude/skills/.pi-map.md
+## children
+-
+## files
+- SKILL.md
+## links
+index: .claude/skills/sift-backlog/.pi-map.index.md
+map: .claude/skills/sift-backlog/.pi-map.md
+## workflows
+-
+## dirty
+-

.claude/skills/sift-backlog/.pi-map.md

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+# .claude/skills/sift-backlog
+dir: .claude/skills/sift-backlog
+
+index: .claude/skills/sift-backlog/.pi-map.index.md
+
+## role
+Defines a workflow skill for triaging, organizing, and activating backlog tasks into actionable plans using a custom CLI tool.
+## files
+- SKILL.md | Defines a workflow skill for triaging, organizing, and activating backlog tasks into actionable plans using a custom CLI tool. | dep: sf (custom CLI tool), task management system, plan management system
+## arch
+Skill-based workflow automation following a structured triage pipeline (scan → filter → prioritize → activate) with CLI tool integration for backlog management.
+## tags
+skill, defines, workflow, triaging, organizing, activating, backlog, tasks
+## symbols
+-
+## workflows
+-
+## dirty
+-