Remove protocol downgrade restriction

[nbolton]

https://symless.atlassian.net/browse/S1-2094

[Copilot]

Pull request overview

This PR adjusts the client/server protocol handshake so the client can negotiate (downgrade) to the server’s reported protocol minor version instead of rejecting older servers.

Changes:

• Removed the client-side isCompatible() compatibility table and related rejection logic.
• Updated Client::handleHello to always respond with helloBackMinor = minor from the server hello.
• Tweaked hello/hello-back log verbosity and messaging.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/lib/client/Client.h	Removes the isCompatible() declaration as part of simplifying handshake logic.
src/lib/client/Client.cpp	Removes compatibility table + rejection path; always negotiates the server’s protocol minor in handleHello.

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

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[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

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[github-actions]

✅ Merge build was successful.
Version: 1.20.1-snapshot+r7
Run: CI (success)