fix: auto-refresh c-display distance formatting

[ascott18]

c-display supported distance formatting (for example :format="{ distance: true }") but did not update itself over time, so relative text like "less than a minute ago" became stale unless parent components manually forced rerenders. This change makes distance displays self-updating in c-display so consumers do not need component-specific timer workarounds.

What changed

• Added adaptive refresh scheduling in c-display for date distance formatting by checking when the rendered formatDistance(...) string would next change, then scheduling a one-shot update at that boundary.
• Scoped this behavior to values that are already valid Date instances; if the value is not a Date, adaptive refresh is skipped.
• Removed the manual setInterval rerender logic from c-admin-editor autosave UI because the shared c-display behavior now covers it.
• Added/updated docs and changelog entries for the new c-display behavior.
• Added a component test that verifies distance-formatted output updates over time.

Notes for reviewers

• Refresh cadence is intentionally adaptive (seconds when needed, then progressively less frequent) to keep relative text accurate while avoiding unnecessary frequent updates for older timestamps.