docs: add AADSTS700046 troubleshooting for Copilot Components in production M365 Copilot

[vystartasv]

Closes #10942

Problem

When a Copilot Component is deployed to production Microsoft 365 Copilot, the component iframe fails during preload with:

AADSTS700046: Invalid Reply Address. Reply Address must have scheme
brk-<tenant-id>:// and be of Single Page Application type.

The same component works correctly in the Copilot Workbench. The issue is that the brk-<tenant-id>://m365.cloud.microsoft redirect URI is not registered on the SharePoint Online Web Client Extensibility Azure AD application.

Fix

Added a Troubleshooting section to the deployment guide with:

• Error identification (error text, symptoms)
• Root cause explanation
• 5-step workaround to register the reply URI in Azure AD
• Preview caveat note

Changes

 docs/spfx/copilot/get-started/build-your-first-copilot-app.md | 24 +++++++++
 1 file changed, 24 insertions(+)

[learn-build-service-prod]

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[learn-build-service-prod]

Learn Build status updates of commit ab700fa:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/spfx/copilot/get-started/build-your-first-copilot-app.md	✅Succeeded	View

For more details, please refer to the build report.

[jansenbe]

@vystartasv / @andrewconnell : this is not the reply URL that should be added. The needed reply URL will be added automatically, let's hold with providing manual workarounds for now.

[andrewconnell]

@jansenbe should this be closed without merging based on your response?