fix(TU-18127): Replace __dangerous-disable-submissions with enable-sandbox=true

[tom-ridsdale]

Summary

https://typeform.atlassian.net/browse/TU-18127

Separate sandbox mode behaviour from submission-disabled mode by introducing a distinct enable-sandbox query parameter.

Problem

Previously, enableSandbox: true in the embed SDK would pass __dangerous-disable-submissions=true to the renderer, causing sandbox mode and submission-disabled mode to be treated identically. This prevents redirects from working in sandboxed embeds.

Solution

Pass enable-sandbox=true instead of __dangerous-disable-submissions=true when enableSandbox is set, allowing the renderer to distinguish between the two flows.

[tf-security]

✅ Snyk checks have passed. No issues have been found so far.

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[typeform-ops-gha]

[BOT] Preview available with hash d60f07879a50b693607024fa2e5ebd4358433489 here.

[sonarqubecloud]

Quality Gate passed

Issues
65 New issues
0 Accepted issues

Measures
1 Security Hotspot
76.5% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[gitstream-cm]

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[typeform-ops-gha]

🎉 This PR is included in version @typeform/embed-v5.5.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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