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-0001-sso-mfa-platform.md

@@ -9,7 +9,8 @@ topic_slug: netkingdom
 state_hub_workstream_id: 39263c4b-ef70-4053-b782-350834b7e1be
 created: "2026-02-28"
 updated: "2026-03-21"
-superseded_by: NK-WP-0003---
+superseded_by: NK-WP-0003
+---
 
 # SSO & MFA Platform — Keycloak + privacyIDEA on Kubernetes