Move best-practices index to BESTPRACTICES.md and document CONTEXT.md pattern

Aligns index files with context-load discovery: BESTPRACTICES.md and CONTEXT.md
now follow the same thin-index pattern as MEMORY.md, auto-loaded at session start.
Adds documentation for both new index types to CLAUDE.md Documentation Standards.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

BESTPRACTICES.md

@@ -0,0 +1,18 @@
+# Best Practices Index
+
+Generalised best practices extracted from real project work. Each topic file is self-contained — read only the files relevant to the current project.
+
+## Topics
+
+- [Validation & Deployment](best-practices/validation.md) — Validate locally, deploy once; full-chain testing; pre-flight checks
+- [Secrets Management](best-practices/secrets-management.md) — SOPS + age, credential handling, file naming, encryption gotchas
+- [Git & Source Control](best-practices/git-source-control.md) — Commit practices, GitOps workflows, remote conventions
+- [Kubernetes Patterns](best-practices/kubernetes.md) — Volume mounts, deployment strategies, naming, bootstrap ordering
+- [Helm Charts](best-practices/helm.md) — Schema validation, version verification, values structure
+- [Ansible](best-practices/ansible.md) — Inventory, templates, idempotency, credential safety
+- [Scripting](best-practices/scripting.md) — Shell conventions, verification scripts, idempotency, colour output
+- [Documentation Standards](best-practices/documentation.md) — CLAUDE.md, MEMORY.md, FUTURE.md, README.md structure and tiered memory
+- [Milestones & Reflections](best-practices/milestones.md) — Milestone workflow, verification, reflection process
+- [Debugging Methodology](best-practices/debugging.md) — Systematic diagnosis, full-chain testing, common pitfalls
+- [Claude Code Skills](best-practices/skills-development.md) — Skill authoring, context injection, tool restrictions
+- [Linting & Formatting](best-practices/linting.md) — Tool choices per language, PostToolUse hook, pre-commit integration, formatter contract