Function parse_binding_entry 

pub fn parse_binding_entry(s: &str) -> Result<BindingEntry, CoreError>

Parse a binding entry string into BindingEntry (eager resolution)

Syntax: task.path [?? default]

• If ?? found outside quotes, splits into path and default
• Default is parsed as JSON literal (strings must be quoted)
• String syntax always produces eager bindings (lazy=false)