Question / Improvement: Incremental publishing of devcontainer features and `devcontainer-collection.json`

## Description

We’re exploring whether the Dev Container CLI is intended to support publishing devcontainer features **one by one**.

When features are published individually, `devcontainer-collection.json` is regenerated each time and ends up containing **only the last published feature**. When all features are published together, the collection file is generated correctly.

This behavior seems consistent and intentional, so this is not a bug report, more a question and possible improvement discussion.

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## Question / Improvement Idea

Is publishing features incrementally an intended workflow?

If this use case is in scope, would it make sense to support:
- Merging newly published features into an existing `devcontainer-collection.json`, or
- A flag or documented approach for incremental publishing?

The motivation is mainly CI/CD robustness, where publishing one feature should not block others.

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If incremental publishing is intentionally unsupported, clarification or documentation around this would also be very helpful.

No files, tests, or entry points are named. Start by reproducing incremental and all-at-once feature publishing, then trace how devcontainer-collection.json is generated; define whether incremental publishing is supported, how entries should be merged, or what documentation should state.

Written by the indexing model from the issue text.