Complete Phase 6: documentation cleanup and integration (#97)

## Summary
- Delete `docs/zk/` directory - all useful content migrated to structured docs
- Delete `docs/README.md` - `docs/index.md` is now the documentation root
- Add `devpi` reference card and `use-pypi-proxy` how-to guide
- Add maintenance notes to `indri` reference (sleep prevention, passwordless sudo)
- Add iCloud Photos backup note to `borgmatic` reference
- Rewrite `zk-docs` mise task to prime AI context with key docs instead of legacy cards
- Update `CLAUDE.md` and `README.md` to remove zk references
- Update `exploring-the-docs` with AI context priming section

This completes the Diataxis documentation restructuring. All six phases are now done.

## Deployment and Testing
- [x] Pre-commit hooks pass (including doc-links validator)
- [ ] Build and deploy to docs.ops.eblu.me to verify rendering

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/97

mise-tasks/zk-docs

@@ -1,15 +1,19 @@
 #!/usr/bin/env bash
-#MISE description="Concatenate all blumeops zettelkasten cards"
+#MISE description="Prime AI context with key BlumeOps documentation"
 
 set -euo pipefail
 
-# Blumeops docs now live in the repo itself (symlinked into zk)
-DOCS_DIR="$(cd "$(dirname "$0")/.." && pwd)/docs/zk"
-MAIN_CARD="$DOCS_DIR/1767747119-YCPO.md"
+DOCS_DIR="$(cd "$(dirname "$0")/.." && pwd)/docs"
 
-# Find all files tagged with blumeops (excluding main card)
-other_cards=$(grep -l '^  - blumeops$' "$DOCS_DIR"/*.md 2>/dev/null | grep -v "$(basename "$MAIN_CARD")" | sort)
+# Key files for AI context priming, in order of importance
+FILES=(
+    "$DOCS_DIR/tutorials/ai-assistance-guide.md"
+    "$DOCS_DIR/reference/index.md"
+    "$DOCS_DIR/how-to/index.md"
+    "$DOCS_DIR/explanation/architecture.md"
+    "$DOCS_DIR/tutorials/index.md"
+)
 
-# Concatenate: main card first, then others
+# Concatenate files with headers showing paths
 # Pass through any args to bat (e.g., --style=header --color=never --decorations=always)
-bat "$@" "$MAIN_CARD" $other_cards
+bat "$@" "${FILES[@]}"