fix(studio): cut sub-agent titles on a rune boundary

The title of a sub-agent chat was cut at a byte count and could end in
the middle of a UTF-8 character. Use the rune-safe CapText. Also use the
slices package for the tool lookup and the waiter removal.

Assisted-by: Claude Code:claude-sonnet-5-5
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

core/services/studio/subagent.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"slices"
 	"strings"
 
 	"github.com/mudler/LocalAI/core/services/studio/agents"
@@ -540,11 +541,9 @@ func (s *Service) forgetWaiter(k string, ch <-chan store.TurnStatus) {
 	s.mu.Lock()
 	defer s.mu.Unlock()
 	ws := s.waiters[k]
-	for i, w := range ws {
-		if (<-chan store.TurnStatus)(w) == ch {
-			s.waiters[k] = append(ws[:i:i], ws[i+1:]...)
-			break
-		}
+	if i := slices.IndexFunc(ws, func(w chan store.TurnStatus) bool { return (<-chan store.TurnStatus)(w) == ch }); i >= 0 {
+		// A copy: notifyWaiters may hold the old slice.
+		s.waiters[k] = slices.Delete(slices.Clone(ws), i, i+1)
 	}
 	if len(s.waiters[k]) == 0 {
 		delete(s.waiters, k)
@@ -643,15 +642,10 @@ func truncate(s string, n int) string {
 	if len(s) <= n {
 		return s
 	}
-	return s[:n] + "…"
+	return session.CapText(s, n) + "…"
 }
 
 // hasTool says whether the list has a tool of that name.
 func hasTool(tools []session.Tool, name string) bool {
-	for _, t := range tools {
-		if t.Name == name {
-			return true
-		}
-	}
-	return false
+	return slices.ContainsFunc(tools, func(t session.Tool) bool { return t.Name == name })
 }

core/services/studio/subagent_internal_test.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"unicode/utf8"
 
 	. "github.com/onsi/ginkgo/v2"
 	. "github.com/onsi/gomega"
@@ -17,6 +18,13 @@ import (
 // A long sub-agent run has more entries than one page; its answer is the last
 // assistant message, not the first page's.
 var _ = Describe("subagent internal", func() {
+	It("cuts a title on a rune boundary", func() {
+		got := truncate("héllo wörld", 2)
+		Expect(utf8.ValidString(got)).To(BeTrue(), "the title %q is cut inside a rune", got)
+		Expect(got).To(Equal("h…"))
+		Expect(truncate("  a   b ", 10)).To(Equal("a b"))
+	})
+
 	It("final text of a long child is its last answer", func() {
 		st, err := store.NewJSON("")
 		Expect(err).NotTo(HaveOccurred())