test: cover PeopleNameFilter empty and case-insensitive matches

Keeps the people-sheet search helper honest without mounting SwiftUI.

bitchatTests/Utils/PeopleNameFilterTests.swift

@@ -0,0 +1,22 @@
+import Testing
+@testable import bitchat
+
+struct PeopleNameFilterTests {
+    @Test func emptyQueryMatchesEverything() {
+        #expect(PeopleNameFilter.matches("alice", query: ""))
+        #expect(PeopleNameFilter.matches("alice", query: "   "))
+    }
+
+    @Test func matchesAreCaseInsensitive() {
+        #expect(PeopleNameFilter.matches("Alice#abcd", query: "ali"))
+        #expect(PeopleNameFilter.matches("Bob", query: "BOB"))
+    }
+
+    @Test func nonMatchingQueryRejects() {
+        #expect(!PeopleNameFilter.matches("alice", query: "bob"))
+    }
+
+    @Test func matchesSubstringInsideNickname() {
+        #expect(PeopleNameFilter.matches("cool_alice", query: "ali"))
+    }
+}