"Remaining req." should reflect budget usage after pre-allocated Copilot Pro+ credits are exhausted

[ericnewton76]

Describe the bug

The Remaining req. indicator in Copilot CLI correctly tracks usage while consuming pre-allocated Copilot Pro+ credits. However, once those allocated credits are exhausted, the experience breaks down in two ways:

1. Errors instead of a clear message — Instead of a friendly notification with actionable guidance, the CLI surfaces raw service errors that are confusing and unhelpful.

2. No budget visibility — If the user has additional spending budgets configured (beyond the pre-allocated credits), the Remaining req. indicator does not transition to showing budget consumption. It effectively goes dark or becomes meaningless after allocated credits run out.

Expected behavior

When pre-allocated credits are exhausted:

• Seamlessly transition the Remaining req. indicator to show budget usage, e.g.: Pro+ Budget (72% remaining)
• If no budget is configured, show: Pre-allocated credits used. Set up a spending budget to continue: [link]
• Do not surface raw backend errors to the user

When running on a configured budget:

• The indicator should show percentage remaining: [budget name] (XX% remaining)
• The backend presumably already reports this data (similar to how it reports pre-allocated usage), so the CLI just needs to consume and display it

Budget clarity:

• When suggesting the user increase budget, specify which budget (there may be multiple) and link to the relevant settings page

Additional context

This likely requires deeper integration with the backend Copilot service's billing/quota APIs. The pre-allocated credits flow already works well — the ask is to extend that same level of visibility and grace into the post-allocation / budget-based usage phase.

The transition from free included credits to paid budget is a critical UX moment. Users need confidence about what they're spending and clear control, not cryptic errors.