feat: harden support, localize knowledge and add operator availability [skip ci]

Source-only publication of reviewed commit 64e96a7f423673dc29ad56485be9fc79bce8af1c.

Passed in isolation: focused frontend/backend tests, race checks, TypeScript typecheck, lint, Go compilation, Flowgram build, and deterministic SDK build/tests.

Not accepted as a production release: Next.js export/native assembly remains blocked by environment memory limits; browser interaction and MySQL staging acceptance remain unverified. No production server, database/schema, runtime configuration, deployment, release tag, or workflow execution was performed.

Expected source tree: 0a4a7528e9.

internal/services/agent_presence_service.go

@@ -0,0 +1,77 @@
+package services
+
+import (
+	"agent-desk/internal/models"
+	"agent-desk/internal/pkg/constants"
+	"agent-desk/internal/pkg/enums"
+	"agent-desk/internal/repositories"
+	"github.com/mlogclub/simple/sqls"
+	"log/slog"
+	"slices"
+	"time"
+)
+
+const agentPresenceLeaseTTL = 90 * time.Second
+const agentPresenceDisconnectGrace = 15 * time.Second
+const agentPresenceRenewInterval = 15 * time.Second
+
+func (s *wsService) renewAgentPresence(session *ClientSession) {
+	if session == nil || session.Closed.Load() || session.Principal == nil || (session.Role != realtimeRoleAdmin && session.Role != realtimeRoleNotification) {
+		return
+	}
+	session.presenceMu.Lock()
+	dispatchPending := false
+	defer func() {
+		session.presenceMu.Unlock()
+		// Finish the presence write before dispatching, and keep ownership in
+		// this call rather than launching an untracked database goroutine.
+		if dispatchPending {
+			_, _ = ConversationDispatchService.DispatchPendingConversations(0)
+		}
+	}()
+	if session.PresenceEnded {
+		return
+	}
+	principal := session.Principal
+	if principal.UserType != enums.UserTypeEmployee || !slices.Contains(principal.Permissions, constants.PermissionConversationView.Code) {
+		return
+	}
+	now := time.Now()
+	last := session.PresenceRenewedAt.Load()
+	if now.Unix()-last < int64(agentPresenceRenewInterval/time.Second) {
+		return
+	}
+	if !session.PresenceRenewedAt.CompareAndSwap(last, now.Unix()) {
+		return
+	}
+	// The internal ID is generated independently per connection, across processes.
+	expires := now.Add(agentPresenceLeaseTTL)
+	if principal.ExpiresAt.Before(expires) {
+		expires = principal.ExpiresAt
+	}
+	lease := models.AgentPresenceLease{ID: session.PresenceLeaseID, UserID: principal.UserID, LoginSessionID: principal.LoginSessionID, ExpiresAt: expires}
+	if lease.ID == "" {
+		return
+	}
+	if err := repositories.SupportAvailabilityRepository.RenewPresence(sqls.DB(), &lease); err != nil {
+		slog.Warn("support presence renewal failed")
+		return
+	}
+	if last == 0 {
+		dispatchPending = true
+	}
+}
+func (s *wsService) endAgentPresence(session *ClientSession) {
+	if session == nil {
+		return
+	}
+	session.presenceMu.Lock()
+	defer session.presenceMu.Unlock()
+	session.PresenceEnded = true
+	if session.PresenceLeaseID == "" || session.PresenceRenewedAt.Load() == 0 {
+		return
+	}
+	if err := repositories.SupportAvailabilityRepository.EndPresence(sqls.DB(), session.PresenceLeaseID, time.Now().Add(agentPresenceDisconnectGrace)); err != nil {
+		slog.Warn("support presence disconnect update failed")
+	}
+}