feat: add Viva Connections ACE reference

[vystartasv]

Summary

• add a local-data React reference for Viva Connections Adaptive Card Extension interaction patterns
• render up to eight validated cards with keyboard interaction and a local detail panel
• document clearly that the implementation is an SPFx web part, not an ACE
• include typed normalization, safe URL handling, tests, verifier, metadata, and ship packaging

Scope and safety

No network calls, Graph permissions, writes, telemetry, secrets, or screenshots. The sample uses local configuration only.

Validation

• npm ci
• npm test — 6 tests passed
• npm run verify — passed before and after build/package
• npm run build — SPFx --ship bundle passed
• npm run package — SPFx --ship package passed
• generated outputs and node_modules removed before commit
• staged diff restricted to samples/react-viva-connections-ace-reference/

Tenant validation requested

Please validate the web part in a representative SharePoint Online tenant and, if useful, adapt the interaction model into an actual Viva Connections ACE. Please provide real tenant screenshots if available; no screenshots are fabricated in this PR.

[vystartasv]

Please validate this sample in a representative SharePoint Online tenant. It is intentionally an SPFx web part, not an ACE: test the local card configuration, keyboard Enter/Space interaction, focus visibility, empty/malformed card handling, eight-card bound, safe HTTP(S) links, and the detail panel. If useful, please adapt the interaction model into a real Viva Connections Adaptive Card Extension and share real tenant screenshots. No screenshots are fabricated in this PR; no network calls, Graph permissions, writes, telemetry, or secrets are used.

[github-actions]

Sample PR validation for #6496

⚠️ Validation status: warnings

We automatically validate all pull requests against our contribution guidance to ensure that all samples provide a consistent experience to our community.

In order to merge this PR in a timely manner, the following criteria must be met:

Validation	Status
Pull request affects only one folder	✅ Succeeded
Sample folder name follows naming convention	✅ Succeeded
README.md contains visitor stat image	⚠️ Warning
Sample requires a .nvmrc file	⚠️ Warning
Sample requires a README.md	✅ Succeeded
Sample requires a screenshot .png in assets folder	⚠️ Warning
No .sppkg file	✅ Succeeded
No node_modules folder	✅ Succeeded
No lib folder	✅ Succeeded
No upgrade reports	✅ Succeeded

@vystartasv please address the above issues and push new changes to this branch.
For more information, see the contribution guidance.

[github-actions]

Sample PR validation for #6496

⚠️ Validation status: warnings

We automatically validate all pull requests against our contribution guidance to ensure that all samples provide a consistent experience to our community.

In order to merge this PR in a timely manner, the following criteria must be met:

Validation	Status
Pull request affects only one folder	✅ Succeeded
Sample folder name follows naming convention	✅ Succeeded
README.md contains visitor stat image	✅ Succeeded
Sample requires a .nvmrc file	✅ Succeeded
Sample requires a README.md	✅ Succeeded
Sample requires a screenshot .png in assets folder	⚠️ Warning
No .sppkg file	✅ Succeeded
No node_modules folder	✅ Succeeded
No lib folder	✅ Succeeded
No upgrade reports	✅ Succeeded

@vystartasv please address the above issues and push new changes to this branch.
For more information, see the contribution guidance.