Function is_failed 

pub fn is_failed(spec_id: &str) -> Result<bool>

Check if a spec has failed.

A spec is considered failed if:

• Status is in_progress
• Agent has exited (no lock file present)
• Some acceptance criteria are still incomplete
• No success signals present (commits matching chant(spec_id): pattern)

Edge cases:

• Agent still running: Returns false
• Spec already finalized/failed: Returns false (status not in_progress)
• Has commits matching chant(spec_id) pattern: Returns false (agent completed work)

Errors

Returns an error if:

• Spec file is unreadable
• Git commands fail