feat(server): add comment CRUD endpoints and issue filter/update enhancements

- Add UpdateComment and DeleteComment handlers with /api/comments/{commentId} routes
- Add broadcast for comment create/update/delete WebSocket events
- Support status, priority, and assignee_id filters on ListIssues
- Extend UpdateIssue to handle due_date, acceptance_criteria, context_refs, repository
- Properly distinguish "field not sent" vs "field sent as null" in UpdateIssue
- Add corresponding SDK methods and TypeScript types

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/cmd/server/router.go

@@ -109,6 +109,12 @@ func NewRouter(pool *pgxpool.Pool, hub *realtime.Hub) chi.Router {
 			})
 		})
 
+		// Comments
+		r.Route("/api/comments/{commentId}", func(r chi.Router) {
+			r.Put("/", h.UpdateComment)
+			r.Delete("/", h.DeleteComment)
+		})
+
 		// Agents
 		r.Route("/api/agents", func(r chi.Router) {
 			r.Get("/", h.ListAgents)