Fixes #36596 - Update existing array variable overrides

[jakduch]

Summary

Fixes #36596.

The host details editor decided whether to create or update an override from the effective value's source. For merged array variables, that source can remain a host group even when a host-specific lookup value already exists. Editing the variable again then attempted to create the same matcher and failed with has already been taken.

Choose the operation from the actual lookup value for the host matcher. Reuse the same lookup-by-matcher rule for deleting overrides, without comparing a stored array to its merged effective value.

Add a regression fixture and test for editing an existing host override whose effective array also contains inherited values.

Testing

• Targeted ESLint passes
• Ansible variable override update and delete suites: 8 tests passed

AI usage disclosure

Per the community discussion on AI policy, the issue was investigated and the changes, tests, and PR wording were prepared with the assistance of Codex 5.6 Sol High. The resulting changes were reviewed before submitting. The commit also includes an Assisted-By trailer.