fix(command): add missing command handler wiring and lint fixes

Wire SetCommandHandler into ChannelInboundProcessor so slash commands
are intercepted before reaching the LLM. Also apply lint fixes across
command package (strconv.Itoa, comment formatting, unused code removal)
and remove obsolete tool-call-browser.vue component.

internal/command/handler_test.go

@@ -29,10 +29,6 @@ type fakeSubagentService struct {
 	items []subagent.Subagent
 }
 
-func (f *fakeSubagentService) list() []subagent.Subagent {
-	return f.items
-}
-
 type fakeScheduleService struct {
 	items []schedule.Schedule
 }
@@ -325,7 +321,7 @@ func TestNewCommands_NilServices(t *testing.T) {
 	}
 }
 
-// suppress unused warnings
+// suppress unused warnings.
 var (
 	_ = fakeSubagentService{items: []subagent.Subagent{{ID: "1", Name: "test", CreatedAt: time.Now(), UpdatedAt: time.Now()}}}
 	_ = fakeScheduleService{items: []schedule.Schedule{{ID: "1", Name: "test"}}}