_record_timezone_migration_catchup was a line-for-line clone of
_record_persisted_error_recovery (counter bump, bounded recent list,
best-effort jsonl append). Extract _append_telemetry_record and route
both through it; one shared history cap replaces the two per-counter
constants. Also correct the "distinct from catch_up_occurrences" comment:
a migrated row that is also past its grace window increments both.
No behavior change; both recorders write the same entries to the same
files.
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