fix: config file key credential-command not recognized (underscore works, hyphen doesn't)

[cboone]

Summary

The CLI flag --credential-command uses a hyphen, but the corresponding config file key only works as credential_command (underscore). The hyphenated form credential-command in ~/.config/fm/config.yaml is silently ignored.

Steps to reproduce

# ~/.config/fm/config.yaml
# This does NOT work:
credential-command: "security find-generic-password -s fm -a fm -w"

# This works:
credential_command: "security find-generic-password -s fm -a fm -w"

# With hyphen form in config:
fm session
# Error: no token configured

# With underscore form in config:
fm session
# Success: Username: cboone@fea.st

Expected behavior

The config file should accept the same key name as the CLI flag (credential-command with a hyphen), or both forms should be accepted.

This is likely a Viper/Cobra configuration binding issue where SetConfigName doesn't normalize hyphens to underscores (or vice versa) when reading the YAML file.