Update docs/azure-devops-task.md

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: tgenov

docs/azure-devops-task.md

@@ -83,9 +83,9 @@ In the example above, the devcontainer-build-run will perform the following step
 | cacheFrom                 | false    | Specify additional images to use for build caching                                                                                                                                                                                                               |
 | noCache                   | false    | Builds the image with `--no-cache` (takes precedence over `cacheFrom`)                                                                                                                                                                                           |
 | cacheTo                 | false    | Specify the image to cache the built image to                                                                                                                                                                                                               |
-| platform                  | false    | Platforms for which the image should be built. If omitted, defaults to the platform of the GitHub Actions Runner. Multiple platforms should be comma separated.                                                                                                  |
-| platformTag               | false    | Tag suffix for this platform build (e.g., `linux-amd64`). Used in matrix builds to push per-platform images that are later merged into a multi-arch manifest.                                                                                                   |
-| mergeTag                  | false    | Comma-separated list of platform tags to merge into a multi-arch manifest (e.g., `linux-amd64,linux-arm64`). Used in the merge job after matrix builds complete.                                                                                                |
+| platform                  | false    | Platforms for which the image should be built. If omitted, defaults to the platform of the GitHub Actions Runner. Multiple platforms should be comma separated. Ignored when `platformTag` is set (matrix mode).                                                |
+| platformTag               | false    | Tag suffix for this platform build (e.g., `linux-amd64`). In matrix builds, this controls which per-platform image is built and tagged; when set, `platform` is ignored. Used to push per-platform images that are later merged into a multi-arch manifest.      |
+| mergeTag                  | false    | Comma-separated list of platform tags to merge into a multi-arch manifest (e.g., `linux-amd64,linux-arm64`). When set, the task skips building an image and instead merges previously built `platformTag` images in the merge job after matrix builds complete. |
 
 ## Outputs