Feature request: configurable past-tense completion verbs

Feature Request

Add a settings.json config key to customize the past-tense verb shown in the completion message (e.g. \"Sautéed for 2m\") after Claude finishes a task.

Current behavior

The completion verb is randomly picked from a hardcoded list in the binary:

\\\
["Baked", "Brewed", "Churned", "Cogitated", "Cooked", "Crunched", "Sautéed", "Worked"]
\\\

There is no way to configure this.

Desired behavior

A completionVerbs key in settings.json mirroring the existing spinnerVerbs API:

\\\json
{
"completionVerbs": {
"mode": "replace",
"verbs": ["Shipped", "Deployed", "Merged"]
}
}
\\\

• "mode": "replace" — use only the provided verbs
• "mode": "append" — add to the built-in set

Why

The spinnerVerbs setting already supports this pattern for present-tense verbs. Extending it to the completion message would give users consistent control over both states.