feat(artifacts): complete generic artifact system with upload handlers, tests, and action integration (#798)

- Add ArtifactUploadHandler with support for github-artifacts, storage (rclone),
  and local copy upload targets, including large file chunking for GitHub Artifacts
- Add 44 unit tests covering OutputTypeRegistry, OutputService, and
  ArtifactUploadHandler (config parsing, upload coordination, file collection)
- Add 6 new action.yml inputs for artifact configuration
- Add artifactManifestPath action output
- Wire artifact collection and upload into index.ts post-build flow

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/model/build-parameters.ts

@@ -106,6 +106,12 @@ class BuildParameters {
   public cacheUnityInstallationOnMac!: boolean;
   public unityHubVersionOnMac!: string;
   public dockerWorkspacePath!: string;
+  public artifactOutputTypes!: string;
+  public artifactUploadTarget!: string;
+  public artifactUploadPath!: string;
+  public artifactCompression!: string;
+  public artifactRetentionDays!: string;
+  public artifactCustomTypes!: string;
 
   public static shouldUseRetainedWorkspaceMode(buildParameters: BuildParameters) {
     return buildParameters.maxRetainedWorkspaces > 0 && Orchestrator.lockedWorkspace !== ``;
@@ -242,6 +248,12 @@ class BuildParameters {
       cacheUnityInstallationOnMac: Input.cacheUnityInstallationOnMac,
       unityHubVersionOnMac: Input.unityHubVersionOnMac,
       dockerWorkspacePath: Input.dockerWorkspacePath,
+      artifactOutputTypes: Input.artifactOutputTypes,
+      artifactUploadTarget: Input.artifactUploadTarget,
+      artifactUploadPath: Input.artifactUploadPath,
+      artifactCompression: Input.artifactCompression,
+      artifactRetentionDays: Input.artifactRetentionDays,
+      artifactCustomTypes: Input.artifactCustomTypes,
     };
   }