Fix roll first-lots display and make market add use pending orders.

Store initial_lots on roll groups, submit market roll as CTP pending legs with cancel closing empty groups, and backfill first-lots for existing active groups.

Co-authored-by: Cursor <cursoragent@cursor.com>

modules/web/templates/strategy.html

@@ -139,7 +139,7 @@
                 <button type="button" class="btn-primary" id="btn-roll-exec" hidden {% if not roll_allowed %}disabled{% endif %}>执行滚仓</button>
             </div>
             <div id="roll-preview" class="strategy-preview" hidden></div>
-            <p class="hint" id="roll-exec-hint" hidden style="font-size:.75rem;margin-top:.45rem">市价加仓：须交易时段内确认，10 秒倒计时执行；突破加仓：休盘也可提交，开盘后再监控触价</p>
+            <p class="hint" id="roll-exec-hint" hidden style="font-size:.75rem;margin-top:.45rem">市价加仓：提交后进入「正在滚仓」挂单，成交后更新持仓；撤单后滚仓组消失。突破加仓：休盘也可提交，开盘触价后自动市价加仓。</p>
             {% if not trading_session %}
             <p class="hint text-muted" id="roll-off-session-hint" style="font-size:.75rem;margin-top:.35rem">当前{{ session_clock.status_label or '休盘' }}：市价加仓须交易时段内执行；休盘可先预览，或选「突破加仓」提交监控。</p>
             {% else %}