feat: add initial

Signed-off-by: kjuulh <contact@kjuulh.io>

todos/SQ-008-protobuf-api-definitions.md

@@ -0,0 +1,42 @@
+# SQ-008: Protobuf API Definitions
+
+**Status:** `[ ] TODO`
+**Blocked by:** SQ-000
+**Priority:** High
+
+## Description
+
+Define all protobuf service definitions and generate the Rust gRPC code via buf.
+
+## Files to Create/Modify
+
+- `interface/proto/sq/v1/data_plane.proto` - Publish, Subscribe, Ack RPCs
+- `interface/proto/sq/v1/control_plane.proto` - CreateTopic, DeleteTopic, ListTopics, DescribeTopic, CreateConsumerGroup
+- `interface/proto/sq/v1/health.proto` - Status service (may already exist from Phase 0)
+- `interface/proto/sq/v1/cluster.proto` - ReplicateEntries, Join, Heartbeat, FetchSegment (internal)
+- `crates/sq-grpc-interface/src/lib.rs` - updated module re-exports
+- Regenerated code in `crates/sq-grpc-interface/src/grpc/`
+
+## Key Service Definitions
+
+### DataPlaneService
+- `Publish(PublishRequest) -> PublishResponse`
+- `Subscribe(SubscribeRequest) -> stream SubscribeResponse`
+- `Ack(AckRequest) -> AckResponse`
+
+### ControlPlaneService
+- `CreateTopic`, `DeleteTopic`, `ListTopics`, `DescribeTopic`, `CreateConsumerGroup`
+
+### ClusterService (internal)
+- `ReplicateEntries`, `Join`, `Heartbeat`, `FetchSegment` (streaming)
+
+### StatusService
+- `Status(GetStatusRequest) -> GetStatusResponse`
+
+## Acceptance Criteria
+
+- [ ] `buf lint` passes on all proto files
+- [ ] `buf generate` produces code in sq-grpc-interface
+- [ ] `cargo check -p sq-grpc-interface` passes
+- [ ] All service traits are generated (DataPlaneService, ControlPlaneService, ClusterService, StatusService)
+- [ ] AckMode enum has ALL, LOCAL, NONE variants