Fix summon menu overwriting active spell target

[nightNR]

• ## Description

Fixes an issue where opening the summon target selection menu overwrote the character’s active action context while another spell was still waiting for its
cast delay.

For targeted summons, m_Act_UID and m_Act_Prv_UID are now left unchanged until the summon target is selected. Non-targeted summons retain the existing behavior
of setting both values to the casting character.

This prevents the summon menu from corrupting the target information of an active spell.

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Type of Change

• Bug fix
• New feature
• Performance improvement
• Refactoring
• Documentation update
• Build / CI change
• Other (please describe)

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Related Issues

None.

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Testing

• Tested on a clean SphereServer instance with latest ScriptPack
• No regressions in existing functionality
• Added or updated tests (if applicable)

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Checklist

• Code compiles successfully
• Changes follow the project's coding style
• No unrelated code was modified
• Documentation updated where necessary (not applicable)
• This PR does not introduce breaking changes

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Additional Notes

The PR consists of one commit and changes only src/game/clients/CClient.cpp.

Local uncommitted changes present in the working tree are not part of this PR.