The sandbox blocks love.system and love.filesystem, which orphans the
native step bridge (#452, #489): its one consumer can no longer call
syncHealthSteps or read steps_pending.json (#1186).
Adds a "steps" manifest permission (shown to the player like the
others) gating a mod.steps facade: available() probes the bridge
quietly, sync() forwards the async refresh, poll() hands the mod its
copy of a delivery. The engine owns the pending file -- mods never name
a path and receive only { steps, from, to }. Without the permission the
acting calls name it, following the network gate. No new events, hooks
or registries; nothing removed.
RFC 0009. Tests: tests/modkit/cases/steps_bridge.lua (no-mod cold
bridge, permissioned sync/poll, per-mod copies, contract-field
filtering, malformed-delivery drop, unpermissioned refusal, bridgeless
build).
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>