AUD-117: derive person from the question via project people list

Decode the people list from each project's /capabilities and set the /ask
person field from a whole-word, case-insensitive name in the question when
the caller did not name a person. Match only the routed project's people,
so a name from another project does not leak across. Fall back to asker
when no name matches.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

src/understand/person.go

@@ -0,0 +1,37 @@
+package understand
+
+import (
+	"regexp"
+	"strings"
+)
+
+// MatchPerson returns the household name from people that appears as a whole
+// word in the question, or "" when no name matches.
+//
+// It is deterministic: no LLM is in this path (AGENTS.md rule 4). The Hub uses
+// it to set the /ask person field from the question when the caller did not
+// name a person. A caller-supplied person always wins; the caller does not call
+// this function in that case.
+//
+// The match is case-insensitive and whole-word, so "harry" matches "What does
+// Harry have on today?" but not "harrypotter". The matched name is returned as
+// the project published it, trimmed.
+func MatchPerson(question string, people []string) string {
+	if strings.TrimSpace(question) == "" || len(people) == 0 {
+		return ""
+	}
+	q := strings.ToLower(question)
+	for _, p := range people {
+		name := strings.TrimSpace(p)
+		if name == "" {
+			continue
+		}
+		// \b is a word boundary in Go's RE2. QuoteMeta keeps a name that
+		// holds a regexp character literal.
+		re := regexp.MustCompile(`\b` + regexp.QuoteMeta(strings.ToLower(name)) + `\b`)
+		if re.MatchString(q) {
+			return name
+		}
+	}
+	return ""
+}