feat: LLM accuracy testing framework with 17-test catalog

Framework runs a category/subcategory test catalog against multiple
LLMs through an OpenAI-compatible endpoint. Deterministic evaluators
score each response. Reports render as table, markdown, or JSON.

internal/eval/regex.go

@@ -0,0 +1,29 @@
+package eval
+
+import (
+	"context"
+	"fmt"
+	"regexp"
+)
+
+// regexEval scores full credit when pattern matches the response.
+type regexEval struct {
+	pattern *regexp.Regexp
+	raw     string
+}
+
+// Regex returns an Evaluator awarding full credit when pattern matches
+// anywhere in the response, zero otherwise. pattern must be a valid RE2
+// expression; it panics on an invalid pattern since evaluators are built
+// once at catalog registration time, not per-request.
+func Regex(pattern string) Evaluator {
+	re := regexp.MustCompile(pattern)
+	return regexEval{pattern: re, raw: pattern}
+}
+
+func (r regexEval) Evaluate(_ context.Context, response string) Score {
+	if r.pattern.MatchString(response) {
+		return Score{Value: 1, Detail: fmt.Sprintf("matched /%s/", r.raw)}
+	}
+	return Score{Value: 0, Detail: fmt.Sprintf("no match for /%s/", r.raw)}
+}