GetYamlConfig was not normalizing key aliases (e.g., sync.branch ->
sync-branch), causing 'bd config get sync.branch' to return 'not set'
even when the value was correctly stored.
SetYamlConfig already normalized keys, but GetYamlConfig did not,
leading to a confusing mismatch where set appeared to work but get
could not find the value.
Added TestGetYamlConfig_KeyNormalization to verify the fix.
Fixes#873