docs: consolidate outstanding docs fixes

[clockwork-labs-bot]

Summary

Consolidates the outstanding docs PRs opened by clockwork-labs-bot into one reviewable PR:

• Fix broken getting started docs links #4958
• Document server-issued token reconnect behavior #5085
• docs: sync C++ skill coverage #5089
• docs: clarify Unreal connection ticking #5097
• docs: fix Unreal ticking and C# generate examples #5112
• docs: clarify Unreal client ticking #5114
• docs: update C# connection callback signatures #5117
• docs: sync C++ language coverage #5127
• docs: use deterministic C# schedule time #5138
• docs: clarify client frame ticking guidance #5165

This combines docs updates for:

• getting-started links
• server-issued auth token reconnect behavior in the Unity tutorial
• C++ module/client language coverage
• Unreal client ticking / FrameTick guidance
• C# connection callback signatures and codegen language spelling
• deterministic schedule-table sample time
• client frame ticking troubleshooting

Validation

• rg -n '^(<<<<<<<|=======|>>>>>>>)' docs crates skills
• git diff --check origin/master...HEAD