[fix] Align trust check with session protocol version

[paul-fresquet]

Summary

• ensure trust checks validate joiners against the session protocol version
• persist the session protocol version from the creator at session creation
• adjust server-side trust check tests for peer-based compatibility

Main modifications

• add protocol version on cloud session data and initialize it from the creator
• change StartTrustCheck to compare joiner version with session version (fallback to creator when missing)
• update unit tests covering protocol-version compatibility scenarios

Implementation approach

• store protocol version on the session to represent the creator's protocol
• use this value as the server-side compatibility gate instead of ProtocolVersion.IsCompatible

[Copilot]

Pull request overview

This PR refactors the trust check mechanism to validate joiners against the session protocol version instead of using a generic compatibility check. The session protocol version is now persisted from the creator at session creation time, providing a consistent baseline for compatibility validation.

• Added a ProtocolVersion property to CloudSessionData to store the session's protocol version
• Modified trust check logic to compare joiner protocol version against the session protocol version (with fallback to creator member's version)
• Updated unit tests to reflect the new protocol version matching behavior

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
CloudSessionData.cs	Adds ProtocolVersion property to store session's protocol version
CreateSessionCommandHandler.cs	Initializes session protocol version from creator's public key info during session creation
StartTrustCheckCommandHandler.cs	Changes trust check to compare joiner version with session version instead of using ProtocolVersion.IsCompatible
StartTrustCheckCommandHandlerTests.cs	Updates tests to set session protocol version and validates new comparison logic
CreateSessionCommandHandlerTests.cs	Adds assertion to verify protocol version is properly initialized during session creation

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[sonarqubecloud]

Quality Gate passed

Issues
1 New issue
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

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