fix(loader): validate signal priors

Co-Authored-By: Virgil <virgil@lethean.io>

loader.go

@@ -3,6 +3,7 @@ package i18n
 import (
 	"errors"
 	"io/fs"
+	"math"
 	"path"
 	"slices"
 	"sync"
@@ -407,7 +408,7 @@ func loadSignalPriors(grammar *GrammarData, priors map[string]any) {
 		}
 		for role, value := range bucket {
 			score, ok := float64Value(value)
-			if !ok {
+			if !ok || !validSignalPriorScore(score) {
 				continue
 			}
 			grammar.Signals.Priors[key][core.Lower(role)] = score
@@ -415,6 +416,10 @@ func loadSignalPriors(grammar *GrammarData, priors map[string]any) {
 	}
 }
 
+func validSignalPriorScore(score float64) bool {
+	return !math.IsNaN(score) && !math.IsInf(score, 0) && score >= 0
+}
+
 func float64Value(v any) (float64, bool) {
 	if v == nil {
 		return 0, false

reversal/tokeniser.go

@@ -17,6 +17,7 @@ package reversal
 
 import (
 	"maps"
+	"math"
 	"strings"
 	"unicode/utf8"
 
@@ -1485,6 +1486,9 @@ func (t *Tokeniser) corpusPrior(word string) (float64, float64, bool) {
 	}
 	verb := bucket["verb"]
 	noun := bucket["noun"]
+	if !validSignalPriorScore(verb) || !validSignalPriorScore(noun) {
+		return 0, 0, false
+	}
 	total := verb + noun
 	if total <= 0 {
 		return 0, 0, false
@@ -1492,6 +1496,10 @@ func (t *Tokeniser) corpusPrior(word string) (float64, float64, bool) {
 	return verb / total, noun / total, true
 }
 
+func validSignalPriorScore(score float64) bool {
+	return !math.IsNaN(score) && !math.IsInf(score, 0) && score >= 0
+}
+
 // hasConfidentVerbInClause scans for a confident verb (Confidence >= 1.0)
 // within the same clause as the token at idx. Clause boundaries are
 // punctuation tokens and clause-boundary conjunctions/subordinators.

types.go

@@ -261,7 +261,7 @@ type SignalData struct {
 	VerbAuxiliaries []string                      // Auxiliaries/modals before verbs: "is", "was", "will", ...
 	VerbInfinitive  []string                      // Infinitive markers: "to"
 	VerbNegation    []string                      // Negation cues that weakly signal a verb: "not", "never", ...
-	Priors          map[string]map[string]float64 // Corpus-derived verb/noun priors for ambiguous words.
+	Priors          map[string]map[string]float64 // Corpus-derived verb/noun priors for ambiguous words, consumed by the reversal tokeniser.
 }
 
 // --- Number Formatting ---