fix(ui): per-key 链复用全局 AUTO 画布；统计周期显示实际窗口

两件事。

一、per-key AUTO 链的 UI 之前自己写了一套表格，只有 model + tier 两列，
比全局 AUTO 编辑器弱：没有拖拽排序、没有每槽位的 quota/period/hours。
这是重复实现且必然漂移。改为复用同一套泳道画布：

- 抽出 buildSortIndex / buildLanes / lanesToRules / renderSortEditor，
  全局编辑器与 per-key 编辑器共用。
- sortState.scope 决定保存目标（null=全局，key=该密钥），persistAuto
  按此分支；空 lane 列表即"恢复继承"，与后端空 PUT 等价。
- 画布查找走 sortCanvasEl()，两个 id 都能解析，否则拖拽在弹窗里静默失效。
- keyAutoClose 必须清 scope，否则关掉弹窗后全局编辑器会存到这个 key。
- 删掉旧的 keyAutoRow/keyAutoAddRow/keyAutoClear。

判据改为断言"复用"而非断言具体实现，并新增两条：
- 关闭弹窗不清 scope（全局编辑器会存错目标）
- per-key 编辑器不再挂载共享画布

二、"周视图总量大于月视图"不是 bug：日历周期并非嵌套。"本周"从周一开始，
所以月初会回溯到上月末几天，本周总量合法地大于本月。实测今天 2026-10-03
（周六）：周窗口 09-28→10-03（6 天，9.2B tokens），月窗口 10-01→10-03
（3 天，4.0B tokens）。

真正的缺陷是看不见这一点。统计页新增"统计区间：YYYY-MM-DD → YYYY-MM-DD
(Nd)"，让周 > 月 自解释。判据钉住这个事实，并做变异验证：把周窗口钳制到
月内（一个看起来很自然的"修复"）会被两条判据同时抓住。

CDP 实测：周视图显示"2026-09-28 → 2026-10-03 (6d)"，月视图显示
"2026-10-01 → 2026-10-03 (3d)"；per-key 编辑器渲染出 36 条泳道 / 226 个
块，与全局编辑器同款。

Co-Authored-By: ModelRouter <noreply@modelrouter.dev>

internal/gateway/stats_period_test.go

@@ -319,3 +319,85 @@ func TestPeriodFromQuery(t *testing.T) {
 		}
 	}
 }
+
+// TestPeriodWeekMayStartBeforeMonth pins a fact that looks like a bug and
+// gets reported as one: the calendar periods are NOT nested.
+//
+// On 2026-10-03 (a Saturday) the ISO week runs Mon 2026-09-28 .. Sat
+// 10-03, while the month window is 10-01 .. 10-03. The week therefore reaches
+// back into the previous month and its total is legitimately LARGER than the
+// month's. Anyone reading only the totals will conclude the aggregator is
+// broken; it is not, and this test exists so a future "fix" that makes the
+// windows nested (e.g. clamping the week to the month) is caught as the
+// regression it would be.
+func TestPeriodWeekMayStartBeforeMonth(t *testing.T) {
+	// Saturday 2026-10-03, UTC.
+	now := time.Date(2026, 10, 3, 12, 0, 0, 0, time.UTC)
+
+	weekFrom := periodStart(PeriodWeek, now)
+	monthFrom := periodStart(PeriodMonth, now)
+
+	weekFromD := time.UnixMilli(weekFrom).UTC()
+	monthFromD := time.UnixMilli(monthFrom).UTC()
+
+	if got := weekFromD.Format("2006-01-02"); got != "2026-09-28" {
+		t.Fatalf("week window start = %s, want 2026-09-28 (the Monday)", got)
+	}
+	if got := monthFromD.Format("2006-01-02"); got != "2026-10-01" {
+		t.Fatalf("month window start = %s, want 2026-10-01", got)
+	}
+	if !weekFromD.Before(monthFromD) {
+		t.Fatal("this test only means anything when the week starts before the month")
+	}
+	// The week must reach strictly further back than the month window does,
+	// otherwise the nesting intuition would hold and the UI note would be noise.
+	if back := monthFromD.Sub(weekFromD).Hours() / 24; back <= 0 {
+		t.Fatalf("week should start at least a day before the month window, got %v days back", back)
+	}
+}
+
+// The same overlap must be visible in the aggregate numbers, not just in the
+// window bounds: a week total larger than a month total is the exact symptom
+// an operator reported.
+func TestPeriodWeekTotalCanExceedMonthTotal(t *testing.T) {
+	dir := t.TempDir()
+	audit := filepath.Join(dir, "audit.jsonl")
+
+	// Two records before the month window (inside this ISO week) and one
+	// inside October.
+	pre := time.Date(2026, 9, 29, 10, 0, 0, 0, time.UTC).UnixMilli()
+	in1 := time.Date(2026, 10, 1, 10, 0, 0, 0, time.UTC).UnixMilli()
+	in2 := time.Date(2026, 10, 3, 10, 0, 0, 0, time.UTC).UnixMilli()
+
+	auditPeriod(t, audit,
+		Req{Time: pre, OK: true, Prompt: 100, Compl: 10},
+		Req{Time: pre + 1000, OK: true, Prompt: 100, Compl: 10},
+		Req{Time: in1, OK: true, Prompt: 50, Compl: 5},
+		Req{Time: in2, OK: true, Prompt: 50, Compl: 5},
+	)
+
+	s := periodStats(t, audit)
+	now := time.Date(2026, 10, 3, 12, 0, 0, 0, time.UTC)
+
+	week := s.PeriodSnapshot(PeriodWeek, "", now)
+	month := s.PeriodSnapshot(PeriodMonth, "", now)
+
+	if week.Total.Reqs != 4 {
+		t.Fatalf("week reqs = %d, want 4 (both September records fall in this ISO week)", week.Total.Reqs)
+	}
+	if month.Total.Reqs != 2 {
+		t.Fatalf("month reqs = %d, want 2", month.Total.Reqs)
+	}
+	if week.Total.Tokens <= month.Total.Tokens {
+		t.Fatalf("week tokens (%d) must exceed month tokens (%d): the week reaches into September",
+			week.Total.Tokens, month.Total.Tokens)
+	}
+	// Day must be a strict subset of both, which is the only nesting that holds.
+	day := s.PeriodSnapshot(PeriodDay, "", now)
+	if day.Total.Reqs != 1 {
+		t.Fatalf("day reqs = %d, want 1", day.Total.Reqs)
+	}
+	if day.Total.Tokens >= month.Total.Tokens || day.Total.Tokens >= week.Total.Tokens {
+		t.Fatal("today must be contained in both the week and the month totals")
+	}
+}