Fix broadcast filters and stabilize string helpers

[themuffinator]

Summary

• correct team message broadcasting so only appropriate clients receive friendly updates
• return stable buffers from timer utilities and validate client lookups to avoid dangling pointers
• harden skin overrides and player config loading to reuse safe storage and free temporary allocations

Testing

• not run

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Codex Task

[chatgpt-codex-connector]

💡 Codex Review

https://github.com/themuffinator/muffmode/blob/13067b4499464bdb26d58c80772b3d6ba28293c6/src/g_utils.cpp#L852-L877
Avoid shared static buffer in G_TimeString

Changing G_TimeString to return a pointer to a single static buffer means consecutive calls overwrite the previous result before the caller has a chance to copy it. Callers such as s1 = G_Fmt("{} ({})", G_TimeString(t, false), G_TimeString(t2, false)).data(); now receive two identical strings, because the second call clobbers the buffer used by the first. The previous implementation returned distinct temporaries so this collision did not occur (even though the pointers were dangling). Consider returning a std::string, passing an output buffer, or documenting that the caller must copy before the next call.

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