# V1 Block 23 — Export Abstraction Layer

**Purpose**: Define Export controller and writer interface.

> **Note for Codex**: Follow tasks exactly; avoid exploratory calls when tasks specify names/files/tests.

## Chunk 23.1 — Export controller contract
Recommended level: **XHIGH**

Status: Complete on 2026-06-26.

### Tasks
1. Add package **`packages/scheduler_export`**.
2. Define abstract class `ExportWriter` with `Future<void> begin(ExportContext)`, `Future<void> writeTask(Task)`, `Future<void> end()`, plus factory registry.
3. Define `ExportController` orchestrating repository queries and writer.
4. Provide context object with `ownerId`, `timezone`, `version`.

### Acceptance criteria
1. JSONWriter and CSVWriter stubs compile and implement interface.
2. Unit test writes small set and verifies output.

### Completed implementation
1. Added package `packages/scheduler_export` with public entry points `export.dart` and `scheduler_export.dart`.
2. Added `ExportContext` carrying `ownerId`, `timezone`, and `version`.
3. Added `ExportWriter`, `ExportWriterFactory`, and `ExportWriterRegistry` with default `json` and `csv` mappings.
4. Added `ExportController` that reads owner-scoped paged tasks through `TaskRepository` and streams them to a writer.
5. Added compiling `JsonExportWriter` and `CsvExportWriter` implementations backed by `StringSink`.
6. Added unit tests for owner-scoped JSON export, CSV output, and custom writer factory registration.
7. Wired export tests into the root test wrapper.

### Verification
1. `dart pub get`: passed.
2. `dart format test/scheduler_core_test.dart packages/scheduler_export`: passed.
3. `cd packages/scheduler_export && dart analyze`: passed, no issues found.
4. `cd packages/scheduler_export && dart test`: passed, 3 tests.
5. `dart analyze`: passed, no issues found.
6. `dart test`: passed, 327 tests.
7. `scripts/test.sh`: not present or not executable.

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