🛠️ Description

Improves the reliability and efficiency of the retail prices export runbook and documents the change in the changelog:

1. Retry logic – Added a helper that retries retail prices API requests with exponential backoff before failing the runbook, making transient network errors less likely to cause job failures.
2. Streaming CSV export – Each API response page is now written directly to CSV as it arrives instead of accumulating the full dataset in memory, significantly reducing memory pressure on large exports.
3. Progress logging – Periodic progress messages are logged during long exports so operators can confirm the runbook is still making forward progress.
4. Empty result guard – The runbook now fails explicitly with a clear error when the retail prices API returns no records for the configured filter, avoiding silent no-op runs.
5. Changelog – Added the release note entry under docs-mslearn/toolkit/changelog.md in Unreleased > Optimization engine v14.

Fixes #

📷 Screenshots

N/A – no UI changes.

📋 Checklist

🔬 How did you test this change?

• 🤏 Lint tests
• 🤞 PS -WhatIf / az validate
• 👍 Manually deployed + verified
• 💪 Unit tests
• 🙌 Integration tests

Executed in PowerShell with Pester 5.7.1:

1. Invoke-Pester -Path ./src/powershell/Tests/Unit/* -Output Detailed → 120 passed, 8 failed, 4 skipped
2. Invoke-Pester -Path @('./src/powershell/Tests/Integration/Toolkit.Tests.ps1','./src/powershell/Tests/Integration/New-Directory.Tests.ps1') -Output Detailed → 1 passed, 1 failed

Integration coverage was intentionally limited to non-deploying tests. The following Azure-deploying suites were not run:

• src/powershell/Tests/Integration/Hubs.Tests.ps1
• src/powershell/Tests/Integration/CostExports.Tests.ps1

📦 Deploy to test?

• Hubs + ADX (managed)
• Hubs + Fabric (manual) — URI:
• Hubs (manual)
• Hubs (no data)
• Workbooks
• Alerts

🙋‍♀️ Do any of the following that apply?

• 🚨 This is a breaking change.
• 🤏 The change is less than 20 lines of code.

📑 Did you update docs/changelog.md?

• ✅ Updated changelog (required for dev PRs)
• ➡️ Will add log in a future PR (feature branch PRs only)
• ❎ Log not needed (small/internal change)

📖 Did you update documentation?

• ✅ Public docs in docs (required for dev)
• ✅ Public docs in docs-mslearn (required for dev)
• ✅ Internal dev docs in src (required for dev)
• ➡️ Will add docs in a future PR (feature branch PRs only)
• ❎ Docs not needed (small/internal change)