Protect digest-pinned packages and refuse partial-inventory pruning

Assistant: codex
Assistant-Model: gpt-6-astra
Assistant-Session: 01a0e241-8285-7a63-8c0c-51c9cb824dc3

docs/forgejo-package-prune.md

@@ -131,3 +131,19 @@ counts (`deleted_count`, `candidate_count`, `skipped_protected_count`, `errors`)
 - `railiance-apps/docs/forgejo-package-registry.md`
 - `docs/forgejo-backup.md`
 - `docs/workload-kv-access-lanes.md`
+
+## Digest-pinned packages
+
+Live/exported references with a valid sha256 digest (including tag@digest) protect
+**every container version of that package**. The reason is
+`protected_digest_package`. This conservative policy covers aliases and child
+manifests without assuming the package API supplies a complete digest mapping.
+Other packages retain normal depth-based cleanup. Additive inventory also retains
+rollback references; removal requires the existing owner review. Storage use may
+grow for digest-pinned packages until a reviewed registry-aware mapping replaces
+this conservative protection.
+
+Malformed Forgejo references stop apply. Incomplete requested cluster inventories
+or failed package listings stop apply before any deletion, even when other package
+lists succeed. Dry-run remains available for inspection. No manual prune execution
+is needed to verify the protection logic.