Render per-tracker bug change description entries.
Review Request #15317 — Created Sept. 17, 2026 and updated
Change description entries stored under
bugs:<id>keys are resolved to
the live tracker when one still exists (even if disabled), and otherwise
fall back to the label snapshot with plain IDs, so history never depends
on the current tracker set. When per-tracker entries exist, they take
the legacy bugs_closed entry's place in the page display.
Verified that change descriptions looked correct.