# CLI API Spec Download Command

## Module
Cli

## Status
IMPLEMENTED

## Description
`stella api spec download` command for retrieving the aggregate OpenAPI specification with checksum/ETag verification, enabling offline API reference consumption.

## Implementation Details
- **Command Handlers**: `src/Cli/StellaOps.Cli/Commands/CommandHandlers.cs` -- partial class containing API spec download handler
- **Command Registration**: `src/Cli/StellaOps.Cli/Commands/CommandFactory.cs` -- registers `api spec download` in command tree
- **Sprint**: SPRINT_0204_0001_0004_cli_iv
- **Commands**:
  - `stella api spec download` -- download the aggregate OpenAPI spec. Options: `--output <path>`, `--format json|yaml`, `--verify` (checksum/ETag verification)

## E2E Test Plan
- [ ] Run `stella api spec download --output ./openapi.json` and verify OpenAPI spec file created
- [ ] Run `stella api spec download --format yaml` and verify YAML format output
- [ ] Run `stella api spec download --verify` and verify checksum/ETag verification passes
- [ ] Run command again and verify ETag caching skips re-download when spec unchanged
- [ ] Verify downloaded spec is valid OpenAPI 3.x format
- [ ] Verify error handling when API server is unreachable