_canonical_issue() strips FK/FK#/FA/FB/FLAG/FIX prefixes and normalizes separators so
duplicate representations of one root cause collapse (e.g. FK1-SELINUX_RESTORECON +
SELINUX-RESTORECON -> selinux_restorecon; FK3-WAL_CHECKPOINT +
CONCURRENT-STORE-CHECKPOINT -> checkpoint_before_exit via an alias map). Per issue only
the most-detailed note is reported. mark_covered now covers ALL uncovered finding coords
(including deduped-away duplicates) so nothing re-reports. Corresponding notes re-tagged:
issue logs -> finding, status notes -> impl (no uncategorized notes remain).