chore: add sbx env file and local kits

[dvdksn]

Signed-off-by: David Karlsson 35727626+dvdksn@users.noreply.github.com

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[docker-agent]

Assessment: 🟢 APPROVE

The three new infrastructure configuration files (.sbxenv.yaml, .sbx/kits/hugo/spec.yaml, .sbx/kits/rumdl/spec.yaml) are well-formed and follow safe practices — pinned versions, SHA256 verification, and set -euo pipefail in install scripts. No documentation content, front matter, Hugo shortcodes, or markdown prose are introduced. No redirects, moved pages, or vendored file edits are involved. No issues found.

[docker-agent]

Assessment: 🟢 APPROVE

The three new sandbox configuration files (.sbxenv.yaml, .sbx/kits/hugo/spec.yaml, .sbx/kits/rumdl/spec.yaml) are well-structured. The install scripts use pinned versions with SHA256 verification, safe curl flags (--proto '=https' --tlsv1.2 -fsSL), single-file tar extraction, and temp-file cleanup. No high or medium issues found.