refactor: make orchestrator engine-agnostic at the typed surface (#26)

Remove Unity-specific licensing fields from orchestrator's typed surfaces
(BuildParameters, OrchestratorConfig, CLI input mapper, build/orchestrate
yargs commands, cli-plugin adapter):

- unitySerial
- unityLicensingServer
- skipActivation

These were vestigial — BuildParameters.create() hardcoded them to empty
strings, no orchestrator service read them for logic. They existed only
to mirror unity-builder's BuildParameters shape, which is exactly the
boundary violation: orchestrator's domain is dispatch + providers, not
engine-specific licensing.

The plugin contract (coreParams: Record<string, any>) is already opaque
and engine-agnostic. The host (unity-builder today, @game-ci/cli in the
future) passes its full BuildParameters object through; orchestrator
reads only generic build context (targetPlatform, projectPath, etc.) and
its plugin-owned config from env/inputs. Engine-specific keys ride in
the dict untouched.

No companion change needed in unity-builder: it continues to construct
its own BuildParameters with whatever fields it wants and pass it as
coreParams. The dict's index signature accepts everything.

Documentation:
- Tracking issue #25 lays out the full architecture, today/future state,
  and migration runway.
- Code comments in plugin-lifecycle.ts, interfaces.ts, build-parameters.ts,
  build.ts, orchestrate.ts, input-mapper.ts, build-parameters-adapter.ts
  reference the issue and explain the boundary intent so the next
  contributor understands why these fields are not (and must not be)
  declared here.

Out of scope (separate cleanups, noted in tracking issue):
- cacheUnityInstallationOnMac / unityHubVersionOnMac in input-mapper
  (Mac runtime install caching, more entangled)
- task-parameter-serializer.ts UNITY_SERIAL well-known-secret list
  (well-known-secrets generalization)
- activate CLI command (Unity-specific legacy helper, leave as-is)

Refs game-ci/unity-builder#739 and game-ci/unity-builder#838 (the user-
facing fix that motivated this boundary cleanup).

Author: frostebite

src/cli-plugin/build-parameters-adapter.ts

@@ -21,9 +21,11 @@ export function createBuildParametersFromCliOptions(options: Record<string, any>
   // ── identity / build settings ─────────────────────────────────────
   bp.editorVersion = options.engineVersion || options.editorVersion || options.unityVersion || '';
   bp.customImage = options.customImage || '';
-  bp.unitySerial = options.unitySerial || process.env.UNITY_SERIAL || '';
-  bp.unityLicensingServer = options.unityLicensingServer || '';
-  bp.skipActivation = options.skipActivation || 'false';
+  // Engine-specific licensing fields (unitySerial, unityLicensingServer,
+  // unityLicensingToolset, skipActivation, ...) are not assigned here.
+  // They flow opaquely through BuildParameters' index signature when the host
+  // populates them; orchestrator does not read them.
+  // See https://github.com/game-ci/orchestrator/issues/25
   bp.runnerTempPath = options.runnerTempPath || process.env.RUNNER_TEMP || '';
   bp.targetPlatform = options.targetPlatform || 'StandaloneLinux64';
   bp.projectPath = options.projectPath || '.';

src/cli/__tests__/commands.test.ts

@@ -87,8 +87,15 @@ describe('CLI commands', () => {
       expect(options['chown-files-to']).toBeDefined();
 
       expect(options['provider-strategy']).toBeDefined();
-      expect(options['skip-activation']).toBeDefined();
-      expect(options['unity-licensing-server']).toBeDefined();
+
+      // Engine-specific licensing flags are intentionally NOT defined on
+      // orchestrator's build command — orchestrator is engine-agnostic.
+      // Hosts (unity-builder action, @game-ci/cli) own those flags and pass
+      // them through to the build container as environment variables.
+      // See https://github.com/game-ci/orchestrator/issues/25
+      expect(options['skip-activation']).toBeUndefined();
+      expect(options['unity-licensing-server']).toBeUndefined();
+      expect(options['unity-licensing-toolset']).toBeUndefined();
     });
 
     it('sets correct default values', () => {