Copilot SKU-level hard budgets [GA]

### Value Prop
Enterprise administrators and billing managers can now set **hard spending limits on Copilot licenses** at the enterprise and organization level, giving them the same budget enforcement capabilities already available for usage-based products like Actions and Codespaces. Instead of relying on soft limits and email notifications that only alert when thresholds are reached, admins can enforce strict caps that prevent teams from exceeding their allocated Copilot budget. This eliminates surprise overages, simplifies financial governance across large organizations, and gives IT leaders confidence that individual business units will only consume the licenses they've been allocated.

### Expected Outcome
Large enterprises managing Copilot across multiple organizations need predictable, enforceable spending controls. Today, license-based products only support soft limits — admins receive notifications at 75%, 90%, and 100% thresholds but the platform does not prevent overages. This gap forces billing managers to manually monitor and intervene, creating operational overhead and financial risk. By introducing hard budgets for Copilot License SKUs, we enable enterprises to set organization-level license caps that are automatically enforced, ensuring each business unit stays within its purchased allocation. This reduces administrative burden, prevents unintentional overuse by one organization at the expense of others, and removes a key blocker for enterprises scaling Copilot adoption with confidence.

This roadmap issue names no repository files, tests, or entry points. Start by clarifying the Copilot license SKU budget-enforcement scope and the enterprise and organization behavior described; done would be a shipped hard-budget capability that prevents license spending from exceeding configured caps.

索引モデルが issue の本文から書いたものです。