Replace nine open-coded `if cx.principal.is_some() {
authz::require(...).await.map_err(...) }` blocks with a single
`authz::script_gate(repo, cx, cap, forbidden_fn, backend_fn)` helper.
The helper enshrines the script-as-gate semantics (anonymous public-
HTTP scripts skip the check) and the AuthzDenied::{Denied,Repo}
mapping in one place — eliminating drift between services.
Call sites migrated:
- kv_service::check_read / check_write
- docs_service::check_read / check_write
- files_service::check_read / check_write
- pubsub_service::check_publish
- queue_service::enqueue
The pubsub_service::mint_subscriber_token path keeps the explicit
match because it does a separate `principal` early-bind for other
validation; converting it would obscure intent.
AUDIT.md anchor: F-Q-003. Depends on F-Q-004 (Backend variant) and
F-Q-005 (Repo-passthrough pattern).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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