Document the platform's actors, boundary-crossing actions, and security
goals/non-goals, organized by trust boundary (T0-T4) per the CNCF
TAG-Security Actors/Actions model. Records the primary trust-boundary
invariant (tenant RBAC grants no HelmRelease/core writes; the aggregated
API server fixes the chart reference server-side) and the two admission
enforcement points (core kube-apiserver vs cozystack-api). Every claim
cites a source file so the model can be re-verified as the code evolves.
Assisted-By: Claude <noreply@anthropic.com>
Signed-off-by: Aleksei Sviridkin <f@lex.la>
