Repo hygiene: fill stack-and-commands, normalize workplan statuses

- Fill .claude/rules/stack-and-commands.md (was an empty TODO template)
- Normalize workplan frontmatter statuses to canonical vocabulary
  (completed/done -> finished) per ADR-001
- Repair glued frontmatter delimiter in NK-WP-0001 (superseded_by line)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

workplans/NK-WP-0006-recursive-platform-identity-security-architecture.md

@@ -4,7 +4,7 @@ type: workplan
 title: Recursive platform identity and security architecture
 domain: infotech
 repo: net-kingdom
-status: done
+status: finished
 owner: Bernd Worsch
 topic_slug: netkingdom
 created: 2026-05-17