fix: restore Intel Mac SMC temperature fallback

The macOS SMC per-core fallback path switched to KeyIndexes[core],
but still formatted it as an integer. That produced keys like TC48
instead of TC0C, so affected Intel Macs reported -1C for core temps.

Format the index as a character to restore the TC0C/TC1C/... fallback keys.

Assisted-by: OpenCode (GPT-5.5)

src/osx/smc.cpp

@@ -101,7 +101,7 @@ namespace Cpu {
 		long long result = getSMCTemp(key);
 		if (result == -1) {
 			// try again with C
-			snprintf(key, 5, "TC%1dC", KeyIndexes[core]);
+			snprintf(key, 5, "TC%1cC", KeyIndexes[core]);
 			result = getSMCTemp(key);
 		}
 		return result;