GAP-2: package config API has no grouped batch with revision token and idempotent scope (D0.1b blocking gap)

[alexeygrigorev]

Blocking gap for D0.1c, found by the D0.1b inventory. The site's core/settings_batch.py provides grouped batch read/update with an optimistic revision token (SettingsRevisionConflict) and an idempotent batch scope (_idempotency_scope(scope, actor_ref)). The released package config API (v0.3.0) offers list/export/import and per-key PUT with no revision token and no batch idempotency. D0.1c must keep settings_batch.py as the writer over package Setting rows, or the package must grow batch support first. Evidence: _docs/adoption/settings-contract-inventory.md GAP-2.