Function ticket_field_changed 

pub fn ticket_field_changed(
    ticket_id: &str,
    mr_title: &str,
    field: &str,
    old: &str,
    new: &str,
    ticket_url: &str,
)

Notify that a tracked field on a linked tracker ticket has changed.

This is a single generic entry point for all ticket field changes. The field parameter is a human-readable label (e.g. "priority", "status"), sourced from [gitlab_tracker_core::TicketChange::field_label].

Using one function instead of per-field functions means that adding a new tracked field in core (e.g. Sprint) requires zero changes to this crate. The orchestrator maps TicketChange variants to this function directly.

Icon selection

Priority changes use "dialog-warning" (yellow); all others use "dialog-information".