fix(awards): apply the reference Prefix where it can actually help

Prefix exists so a field holding a bare value counts for an award whose codes
carry a letter: a French operator writes "74" in STATE, DDFM's codes are "D74".
Def's own doc says exactly that. But searchOne applied the prefix AFTER looking
the token up in the reference list — after the step that had just failed — so
the bare form matched nothing and the prefix decorated an empty result. The only
way through was a regex, in a mode where the operator had chosen "code" and
explicitly not "pattern".

The token lookup now tries the prefixed form when the bare one is not a known
reference. The list stays the authority: an unknown number still matches
nothing, so the prefix completes references rather than inventing them.

Second bug in the same pass: the blanket prefix also hit codes that came
straight OUT of the list, so a field already holding "D74" produced "DD74" as
soon as a prefix was configured — for both the token lookup and the
description matcher. Branches that yield whole codes are now excluded from it;
the ones that yield a raw capture (regex, whole-field split) still get it.

internal/award/prefix_test.go

@@ -0,0 +1,81 @@
+package award
+
+import (
+	"testing"
+
+	"hamlog/internal/qso"
+)
+
+// ddfmLike is a small stand-in for the French departments award: predefined
+// references whose codes carry a letter the operator does not type.
+func ddfmLike() []Def {
+	return []Def{{
+		Code: "DDFM", Name: "Departments", Type: TypeQSOFields,
+		Field: "state", MatchBy: "code", Prefix: "D",
+	}}
+}
+
+func ddfmRefs() map[string][]RefMeta {
+	return map[string][]RefMeta{"DDFM": {
+		{Code: "D29", Name: "Finistère", Valid: true},
+		{Code: "D49", Name: "Maine-et-Loire", Valid: true},
+		{Code: "D74", Name: "Haute-Savoie", Valid: true},
+	}}
+}
+
+func refsOf(t *testing.T, defs []Def, q qso.QSO) []string {
+	t.Helper()
+	res := Compute(defs, []qso.QSO{q}, ddfmRefs(), nil)
+	if len(res) != 1 {
+		t.Fatalf("want 1 result, got %d", len(res))
+	}
+	var out []string
+	for _, r := range res[0].Refs {
+		if r.Worked {
+			out = append(out, r.Ref)
+		}
+	}
+	return out
+}
+
+// The reported case: the operator writes just "74" in STATE, the award's codes
+// are "D74", match-by is "code" and a Prefix of "D" is set. That found nothing —
+// the prefix was applied only AFTER the list lookup, i.e. after the step that
+// had already failed — so the only workaround was a regex, in a mode where the
+// operator had explicitly chosen "code" rather than "pattern".
+func TestPrefixCompletesABareReference(t *testing.T) {
+	got := refsOf(t, ddfmLike(), qso.QSO{Callsign: "F5AYE", State: "74"})
+	if len(got) != 1 || got[0] != "D74" {
+		t.Errorf("bare state 74 with prefix D → %v, want [D74]", got)
+	}
+}
+
+// And a field that ALREADY holds the whole code must not be prefixed twice.
+// The blanket pass turned "D74" into "DD74" whenever a prefix was configured.
+func TestPrefixDoesNotDoubleUpOnACompleteCode(t *testing.T) {
+	got := refsOf(t, ddfmLike(), qso.QSO{Callsign: "F5AYE", State: "D74"})
+	if len(got) != 1 || got[0] != "D74" {
+		t.Errorf("state D74 with prefix D → %v, want [D74]", got)
+	}
+}
+
+// A token that is neither a code nor a prefixable one stays unmatched: the
+// prefix must not invent references.
+func TestPrefixDoesNotInventReferences(t *testing.T) {
+	if got := refsOf(t, ddfmLike(), qso.QSO{Callsign: "F5AYE", State: "99"}); len(got) != 0 {
+		t.Errorf("unknown department 99 → %v, want none", got)
+	}
+}
+
+// Without a prefix nothing changes: a bare number matches nothing, a full code
+// matches itself.
+func TestNoPrefixKeepsExactCodeMatching(t *testing.T) {
+	defs := ddfmLike()
+	defs[0].Prefix = ""
+	if got := refsOf(t, defs, qso.QSO{Callsign: "F5AYE", State: "74"}); len(got) != 0 {
+		t.Errorf("no prefix, state 74 → %v, want none", got)
+	}
+	if got := refsOf(t, defs, qso.QSO{Callsign: "F5AYE", State: "D74"}); len(got) != 1 || got[0] != "D74" {
+		t.Errorf("no prefix, state D74 → %v, want [D74]", got)
+	}
+}