[WIP] Add missing C8Run 8.9 changes to release announcements

[Claude]

closes: #8563

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

---

This section details on the original issue you should resolve

<issue_title>Add missing C8Run 8.9 changes to release announcements</issue_title>
<issue_description>## Description

Several C8Run changes for 8.9 are missing from the release announcement docs (890-announcements.md, whats-new-in-89.md, 890-release-notes.md). The code/CLI changes have landed and the product docs are updated (PRs #8506, #8353, #8530), but the release announcements do not call them out as breaking changes or notable changes for upgrading users.

Related issues and PRs:

• C8Run 8.9 – Separate Docker Compose distribution from C8Run camunda#48958 – Separate Docker Compose distribution from C8Run
• C8Run 8.9 – Remove bundled Elasticsearch camunda#48957 – Remove bundled Elasticsearch from C8Run

Missing items

1. --docker flag removed from C8Run (Breaking change — 890-announcements.md)

The --docker flag and Docker Compose bundling have been completely removed from C8Run in 8.9. Users who relied on ./c8run start --docker to run Camunda via Docker Compose will get an error.

Docker Compose is now a standalone artifact available via GitHub releases and the Camunda Download Center.

This was explicitly called out as a release announcement requirement in the acceptance criteria of camunda/camunda#48958:

"Release announcement - Communicate the breaking change clearly (Docker Compose separation from C8Run)."

Suggested addition to 890-announcements.md under # Data:

Breaking change

### Camunda 8 Run: Docker Compose support removed

The `--docker` flag and bundled Docker Compose files have been removed from Camunda 8 Run in 8.9. Camunda 8 Run and Docker Compose are now separate distribution artifacts.

**Action:** If you previously started Docker Compose via `./c8run start --docker`, download the standalone [Docker Compose distribution](/self-managed/quickstart/developer-quickstart/docker-compose.md) from GitHub releases or the Camunda Download Center and run it independently.

2. --disable-elasticsearch flag removed from C8Run (Breaking change — 890-announcements.md)

With Elasticsearch no longer bundled in C8Run, the --disable-elasticsearch flag has been removed. The announcements mention ES is no longer bundled but don't call out this specific CLI flag removal.

Suggested addition to 890-announcements.md (same section or extend the existing H2/ES entry):

The `--disable-elasticsearch` flag is also removed, as Elasticsearch is no longer bundled. To use Elasticsearch as secondary storage, configure an external instance via `--config` and the `application.yaml`.

3. Docker Compose removal mentioned in whats-new-in-89.md and 890-release-notes.md

Neither of these docs mention the Docker Compose separation. The whats-new-in-89.md C8Run section should note that Docker Compose is no longer part of C8Run, and 890-release-notes.md should have a corresponding entry.

4. (Nice to have) Startup URL change

C8Run now opens Operate on startup instead of the quickstart documentation page (camunda/camunda#48285). This is a UX change (not breaking) but worth a mention in the release notes under the "Streamlined local setup" section for completeness.

When should this change go live?

This is a bug fix, security concern, or something that needs urgent release support.
(add bug or support label)

PR Checklist

• docs/reference/announcements-release-notes/890/890-announcements.md — Add Docker Compose removal and --disable-elasticsearch flag removal as breaking changes
• docs/reference/announcements-release-notes/890/whats-new-in-89.md — Mention Docker Compose separation in C8Run section
• docs/reference/announcements-release-notes/890/890-release-notes.md — Add entry for Docker Compose separation</issue_description>

<agent_instructions>Double check the announcements are not already made. Also make sure that this PR https://github.com/camunda/camunda-docs/pulls/dmytrivv2 can be closed with the PR you are creating.</agent_instructions>

Comments on the Issue (you are @claude[agent] in this section)

[github-actions]

👋 🤖 🤔 Hello, @claude! Did you make your changes in all the right places?

These files were changed only in docs/. You might want to duplicate these changes in versioned_docs/version-8.8/.

• docs/reference/announcements-release-notes/890/890-announcements.md
• docs/reference/announcements-release-notes/890/890-release-notes.md
• docs/reference/announcements-release-notes/890/whats-new-in-89.md

You may have done this intentionally, but we wanted to point it out in case you didn't. You can read more about the versioning within our docs in our documentation guidelines.