Prevent a warning being printed when parsing config

[SUSTAPLE117]

Added after the #60 fix so we don't see a warning when it tries to parse the binary itself as a config file

[Copilot]

Pull request overview

This PR prevents Viper’s config auto-discovery from matching an extensionless file named bagel (notably the ./bagel binary when running from its directory), which previously caused YAML parse warnings/errors during config loading.

Changes:

• Stop calling SetConfigType("yaml") during config auto-discovery so only bagel.<ext> files are considered.
• Add a regression test intended to ensure the extensionless bagel binary is not parsed as config.
• Mirror the same “no SetConfigType” behavior in CLI startup config initialization.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
pkg/config/config.go	Removes SetConfigType during auto-discovery to avoid matching an extensionless bagel file (the binary).
pkg/config/config_test.go	Adds a regression test for the extensionless-binary matching scenario (currently needs adjustment to assert on the real log message).
cmd/bagel/root.go	Removes SetConfigType from CLI initConfig auto-discovery path and documents rationale.

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