Populate best practices from claude-foundations

Migrates 20 topic files from claude-foundations/best-practices/ to this
standalone repo. Adds BESTPRACTICES.md index, CLAUDE.md conventions, and
updated README.md. Container agents clone this repo to /best-practices.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

helm.md

@@ -0,0 +1,25 @@
+# Helm Charts
+
+## Schema Validation
+
+- **Always validate values against the chart schema before committing.** Run `helm show values <repo>/<chart> --version <ver>` to check the actual structure.
+- Helm chart schemas change between versions — field names and nesting can differ from documentation or online examples.
+- A quick `helm template` test locally catches schema errors before deployment.
+- `additionalProperties: false` in chart schemas means any extra keys at the wrong nesting level cause a hard failure.
+
+## Version Verification
+
+- Run `helm search repo` or check upstream docs to confirm latest stable versions
+- Don't rely on memory for chart versions — they go stale quickly
+- Check compatibility matrices between chart version, app version, and other cluster components
+
+## Multi-Source Applications
+
+- ArgoCD multi-source Applications use `$ref` syntax to combine external Helm charts with Git-stored values files
+- Keep values files in Git alongside the ArgoCD Application manifest
+
+## Timeout Handling
+
+- Under cluster pressure (many events, etcd busy), default Helm timeouts may not be enough
+- Increase timeout for initial installs (e.g., 10m instead of 5m)
+- `helm upgrade --install` is idempotent — retries are safe