Fix grammatically awkward cooldown message

[ggfevans]

Description

The cooldown error message in GitHubRequestRunner.swift has awkward grammar:

Current: "Cooling down until in 10 secs."

The "until in" construction is grammatically incorrect.

Location

Sources/RepoBarCore/API/GitHubRequestRunner.swift:55

Proposed Fix

Change to: "Cooldown active; retry in 10 sec."

This:

• Matches the internal logging style ("Cooldown active for..." on line 52)
• Works naturally with RelativeFormatter output ("in 10 sec", "in 2 min", etc.)
• Is concise and clear

Code Change

// Line 55, change from:
message: "Cooling down until \(RelativeFormatter.string(from: cooldown, relativeTo: Date()))."

// To:
message: "Cooldown active; retry \(RelativeFormatter.string(from: cooldown, relativeTo: Date()))."