feat: separate worker disabled state from worker version

[jtuglu1]

Description

Currently, to disable a worker (MM/Indexer), you need to set the version as "". This is not ideal, as it's difficult to see a) what version a disabled worker is and b) write any logic to perform scaling around multi-version worker deployments (for example during a rolling upgrade).

This ensures the disabled state is tracked separately from the worker version. The change is backwards compatible (to not break existing deployments) and can then be migrated to simply relying on the disabled flag in a subsequent release.

Release note

Track the worker enabled state separately from the worker version.

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This PR has:

• been self-reviewed.
  • using the concurrency checklist (Remove this item if the PR doesn't have any relation to concurrency.)
• added documentation for new or modified features or behaviors.
• a release note entry in the PR description.
• added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
• added or updated version, license, or notice information in licenses.yaml
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• added integration tests.
• been tested in a test Druid cluster.

[FrankChen021]

I have reviewed the code for correctness, edge cases, concurrency, and integration risks; no issues found.

Reviewed 10 of 10 changed files.

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This is an automated review by Codex GPT-5.5

[abhishekrb19]

Lgtm, left some minor comments.

[FrankChen021]

Severity	Findings
P0	0
P1	0
P2	1
P3	0
Total	1

Reviewed 10 of 10 changed files.

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This is an automated review by Codex GPT-5.5

[FrankChen021]

[P2] Update console disabled checks for preserved worker versions

This now builds the disabled HRTR Worker with its real version instead of the legacy empty string, so /druid/indexer/v1/workers can serialize disabled workers as { disabled: true, version: "v1" }. The web console still checks worker.version === '' in services-view.tsx for both the Disabled label and Enable/Disable action selection, so HRTR-disabled workers will appear enabled and the UI will offer Disable instead of Enable. Update the console WorkerInfo type and checks to use worker.disabled, with version === '' retained as a legacy fallback.