fix: include juniors in payment-inference roster

infer_payments was building member_names from get_members_with_fees()
(adults sheet only). Junior-only members were invisible to the matcher,
so a payment message containing an exact junior name would produce a
fuzzy review match against a different adult sharing the same first name.

Fix: union the adult and junior rosters (deduped via canonical_member_key)
so all members are candidates. The existing exact-name short-circuit in
match_members then handles precedence correctly.

Two regression tests added for the Jáchym Kubík / Jáchym Hrušák case.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## 2026-05-06 16:38 CEST — fix: include juniors in payment-inference roster
+
+- `scripts/infer_payments.py`: union adults + junior rosters so junior-only members are visible to the matcher.
+- Root cause: `get_members_with_fees()` reads only the adults sheet; junior-only kids like Jáchym Kubík were absent from `member_names`, causing the exact-match short-circuit to never fire and a different adult sharing the first name to win via fuzzy review.
+- Two regression tests added to `tests/test_match_members.py`.
+
 ## 2026-05-06 13:18 CEST — feat(go/M2.7-2.9): port domain/matching package
 
 - New `go/internal/domain/matching` package porting three helpers from `scripts/match_payments.py`.