fix(chart): keep zero-year chara and ephemeris dates apart

A zero-year Chara period is shown as 0 years instead of failing the whole chart. Switching ephemeris dates drops the previous day immediately and can be retried. Missing birth data links to chart settings.

frontend/src/lib/chart-view-contract.ts

@@ -86,6 +86,9 @@ export const chartViewPeriodSchema = z.object({
 export const chartViewMahadashaSchema = chartViewPeriodSchema.extend({
   sign: z.string().nullable(),
   antardashas: z.array(chartViewPeriodSchema),
+  // Present only for a Chara mahadasha whose engine duration is exactly 0.
+  // It stays on the list, occupies no timeline, and has no antardashas.
+  zeroYear: z.literal(true).optional(),
 });
 
 export const chartViewDashaTrackSchema = z.object({

frontend/src/lib/chart-view-labels.ts

@@ -140,6 +140,10 @@ export const ANTARDASHA_DERIVED_NOTE = "分运按标准比例从大运边界推
 
 export const CHARA_ANTARDASHA_DATE_NOTE = "分运时长来自引擎的十二等分；起止日期按大运边界推算，不是引擎单独返回的日历字段。";
 
+export const CHARA_ZERO_YEAR_LABEL = "0 年";
+
+export const CHARA_ZERO_YEAR_NOTE = "本段时长为 0，不展开";
+
 export const WESTERN_UNAVAILABLE_COPY = "西洋盘这一栏要等回归黄道端点上线。现在还没有，先空着——不会拿印度盘的度数改写成回归黄道。";
 
 export const QIZHENG_UNAVAILABLE_COPY = "七政四余这一栏要等宿度端点上线。现在还没有，先空着。";
@@ -161,6 +165,8 @@ export const CHART_VIEW_COPY = {
   waitingVarga: "这一分盘还没拿到。",
   unauthenticated: "请先登录后再看星盘。",
   incomplete: "还没有可用来排盘的出生资料。把日期、时间和地点填进星盘资料后，打开就能看见盘。",
+  profileEntryTitle: "还没有星盘资料",
+  profileEntryAction: "去填写出生资料",
   profileQueryError: "星盘资料这会儿读不出来，我们已经记录下来了。",
   adoptedIncomplete: "已采用的出生时间缺了排盘要用的时区，这张盘先不能算。我们已经记录下来了。",
   timezoneFailure: "出生地的时区没有对上，这张盘先不能算。我们已经记录下来了。",

frontend/src/lib/chart-view-mapper.ts

@@ -82,11 +82,19 @@ function isoDay(value: string): string {
 function addWeightedSpan(startIso: string, endIso: string, index: number, weights: readonly number[]): { start: string; end: string } {
   const start = Date.parse(`${startIso}T00:00:00Z`);
   const end = Date.parse(`${endIso}T00:00:00Z`);
-  const total = weights.reduce((sum, weight) => sum + weight, 0);
-  const before = weights.slice(0, index).reduce((sum, weight) => sum + weight, 0);
+  const total = weights.reduce((sum, weight) => sum + (Number.isFinite(weight) ? weight : 0), 0);
+  // A zero-year Chara mahadasha gives every antardasha weight 0. `??` does not
+  // replace 0, so total is 0 and `before / total` is NaN. Never call
+  // `Date#toISOString` on that — it throws RangeError and fails the whole chart.
+  if (!Number.isFinite(start) || !Number.isFinite(end) || !(total > 0)) {
+    return { start: startIso, end: startIso };
+  }
+  const before = weights.slice(0, index).reduce((sum, weight) => sum + (Number.isFinite(weight) ? weight : 0), 0);
+  const weight = Number.isFinite(weights[index]) ? weights[index]! : 0;
   const span = end - start;
   const from = start + span * (before / total);
-  const to = index === weights.length - 1 ? end : start + span * ((before + weights[index]!) / total);
+  const to = index === weights.length - 1 ? end : start + span * ((before + weight) / total);
+  if (!Number.isFinite(from) || !Number.isFinite(to)) return { start: startIso, end: startIso };
   return { start: new Date(from).toISOString().slice(0, 10), end: new Date(to).toISOString().slice(0, 10) };
 }
 
@@ -390,12 +398,16 @@ function charaTrack(charaPacket: Record<string, unknown> | null, birthDate: stri
     if (!row) return [];
     const sign = text(row.sign);
     const lord = text(row.lord) ?? sign ?? "—";
-    const duration = finite(row.duration_years) ?? 1;
+    const rawDuration = finite(row.duration_years);
+    const duration = rawDuration === null ? 1 : rawDuration;
+    const zeroYear = duration === 0;
     const start = cursor;
     const end = addYears(start, duration);
     cursor = end;
     const rawAntar = Array.isArray(row.antardashas) ? row.antardashas : [];
-    const antardashas = rawAntar.length > 0
+    const antardashas = zeroYear
+      ? []
+      : rawAntar.length > 0
       ? rawAntar.flatMap((antar, index) => {
         const item = record(antar);
         if (!item) return [];
@@ -430,6 +442,7 @@ function charaTrack(charaPacket: Record<string, unknown> | null, birthDate: stri
       end,
       current: containsDay(start, end, asOf),
       derived: false,
+      ...(zeroYear ? { zeroYear: true as const } : {}),
       antardashas,
     }];
   });

frontend/src/lib/ephemeris-view.ts

@@ -19,7 +19,9 @@ export const EPHEMERIS_COPY = {
   transitsUnavailable: "这一天的行运还没拿到。",
   natalMissing: "还没有本命上升，相对本命这一列空着。",
   eventsHeading: "未来九十天",
+  eventsPending: "换座和停滞还在取。",
   eventsUnavailable: "换座和停滞还没接上。这一页其余部分不受影响。",
+  dateFailed: "这一天的星历没取到，点日期再试一次。",
   ask: "带这天去提问",
   loginTitle: "请先登录",
   loginBody: "登录后即可查看星历。",

frontend/src/lib/settings-url.ts

@@ -3,12 +3,14 @@ import type { BillingPaneTab, MembershipPlanAlias } from "@/lib/membership";
 export const SETTINGS_QUERY_KEY = "settings";
 
 export type SettingsQuery = {
-  readonly pane: "billing";
+  readonly pane: "billing" | "chart";
   readonly source: string | null;
   readonly plan: MembershipPlanAlias | null;
   readonly tab: BillingPaneTab | null;
 };
 
+export const CHART_SETTINGS_HREF = "/?settings=chart";
+
 const PLAN_ALIASES: ReadonlySet<string> = new Set(["trial", "monthly", "yearly"]);
 const BILLING_TABS: ReadonlySet<string> = new Set(["membership", "credits", "redeem", "orders"]);
 
@@ -18,7 +20,9 @@ function searchParams(search: string) {
 
 export function parseSettingsQuery(search: string): SettingsQuery | null {
   const params = searchParams(search);
-  if (params.get(SETTINGS_QUERY_KEY) !== "billing") return null;
+  const pane = params.get(SETTINGS_QUERY_KEY);
+  if (pane === "chart") return { pane: "chart", source: null, plan: null, tab: null };
+  if (pane !== "billing") return null;
   const planRaw = params.get("plan");
   const tabRaw = params.get("tab");
   return {