refactor: extract chime--render-modeline-string from chime--update-modeline

chime--update-modeline grew to mix orchestration with the modeline-string formation logic. Extract the formation block into its own helper so the orchestrator reads as pure orchestration: build upcoming, find soonest, render, force update.

The helper handles both branches. When a soonest event is in the modeline window, format and propertize via chime--propertize-modeline-string. Otherwise, when chime-modeline-no-events-text is set, propertize that with the appropriate tooltip and click handlers (mouse-1 always, mouse-3 only when there are upcoming events to jump to).

The orchestrator drops from 45 to 25 lines.

0 files changed, 0 insertions, 0 deletions