[AZ-1074] [AZ-1075] gRPC tile stream tests and shared proto

Extract tile_provision.proto into GrpcContracts, add integration
tests and validation hardening for DeliverRouteTiles streaming.

Co-authored-by: Cursor <cursoragent@cursor.com>

_docs/02_tasks/done/AZ-1074_grpc_tile_stream_service.md

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+# gRPC TileStream Service for Route-Based Tile Delivery
+
+**Task**: AZ-1074_grpc_tile_stream_service
+**Name**: gRPC TileStream Service
+**Description**: Add gRPC streaming endpoint that delivers route tiles as they become available.
+**Complexity**: 5 points
+**Dependencies**: RouteService, tile storage, Google Maps downloader
+**Component**: SatelliteProvider.Api
+**Tracker**: AZ-1074
+**Epic**: AZ-115
+
+## Problem
+
+Consumers (gps-denied-onboard) can poll REST `POST /api/satellite/route` until `mapsReady`. No streaming transport exists for progressive tile delivery.
+
+## Outcome
+
+- gRPC `StreamTiles(RouteTileRequest) returns (stream TileChunk)` alongside existing REST.
+- Reuses `RouteService` and tile download pipeline.
+- Proto contract checked into repo.
+
+## Scope
+
+### Included
+- `satellite_provider.proto` with route waypoints, region size, zoom, optional geofences.
+- Stream messages: tile id, lat/lon, zoom, image bytes or path + checksum, status, terminal summary.
+- ASP.NET Core gRPC host on configurable port.
+- Happy-path + invalid-request integration test in `SatelliteProvider.IntegrationTests`.
+
+### Excluded
+- Mission cache package assembly (COG/manifest/FAISS).
+- Removing or changing REST endpoints.
+- Imagery source migration off Google Maps.
+
+## Acceptance Criteria
+
+**AC-1: Happy path streams tiles**
+Given a valid 2-point route
+When a client calls `StreamTiles`
+Then at least one `TileChunk` arrives before `StreamComplete`.
+
+**AC-2: Cache reuse**
+Given tiles already in DB cache
+When the stream runs
+Then cached tiles are served without redundant Google Maps download.
+
+**AC-3: Invalid route rejected**
+Given zero waypoints or out-of-range coordinates
+When the client calls `StreamTiles`
+Then gRPC returns `INVALID_ARGUMENT` with details.
+
+**AC-4: Backpressure safe**
+Given a slow consumer
+When tiles stream
+Then tile bytes are not corrupted.
+
+## Constraints
+
+- gRPC is additive; REST remains supported.
+- Blocks gps-denied-onboard AZ-1076 consumer.

_docs/02_tasks/done/AZ-1075_grpc_tile_stream_integration_tests.md

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+# gRPC TileStream Blackbox Integration Tests
+
+**Task**: AZ-1075_grpc_tile_stream_integration_tests
+**Name**: gRPC TileStream Integration Tests
+**Description**: Blackbox tests for the gRPC tile stream against a running service container.
+**Complexity**: 3 points
+**Dependencies**: AZ-1074
+**Component**: SatelliteProvider.IntegrationTests
+**Tracker**: AZ-1075
+**Epic**: AZ-284
+
+## Problem
+
+AZ-284 blackbox suite covers HTTP API only. The new gRPC tile stream has no automated coverage.
+
+## Outcome
+
+- Integration tests exercise `StreamTiles` end-to-end in `docker-compose.tests.yml`.
+- Failure cases assert correct gRPC status codes.
+- Metadata consistency with REST route endpoint verified for same route.
+
+## Scope
+
+### Included
+- Fixture: API + Postgres via existing docker-compose.
+- Happy path: route → tiles → stream complete.
+- Failure cases: empty route, invalid coordinates, zoom out of range.
+- Cross-check with `GET /api/satellite/route/{id}` metadata.
+
+### Excluded
+- Consumer-side tests (gps-denied-onboard AZ-1076).
+- Performance/load testing.
+
+## Acceptance Criteria
+
+**AC-1: Pipeline green**
+Given docker-compose test run
+When gRPC happy-path test executes
+Then it passes with full verbosity (`-v`, no quiet mode).
+
+**AC-2: Failure status codes**
+Given each invalid request variant
+When the gRPC client calls `StreamTiles`
+Then the expected gRPC status code is returned.
+
+**AC-3: REST consistency**
+Given the same route submitted via REST and gRPC
+When both complete
+Then tile metadata is consistent.
+
+## Constraints
+
+- Depends on AZ-1074 landing first.
+- Follow existing integration test patterns in `SatelliteProvider.IntegrationTests`.