fix(aci): Gracefully handle missing actions in Alerts UI

[malwilley]

Closes ISWF-2365

When an action is no longer available, we were previously rendering null, which made it impossible to get the alert in a working state for saving. This PR renders an item which can be removed with a helpful message telling the user to add a new action.

Before:

After:

[linear-code]

ISWF-2365 Show broken Slack action when integration is inactive

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[cursor]

API failure misreported as permanently unavailable actions

Medium Severity

When the useAvailableActionsQuery call fails (network error, 500, etc.), isLoadingActions becomes false and availableActions defaults to []. This causes getActionHandler to return undefined for every action, triggering the "no longer available" error message for all of them. Users could then be misled into deleting perfectly valid actions. The code checks isLoadingActions but not isError from the query, so a transient API failure is indistinguishable from a genuinely removed integration.

 

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