fix(frontend): restore dates on session detail entry

A direct session detail route initializes the same filtered sidebar as the Sessions dashboard. Apply explicit or linked date state at the route-entry boundary so the first sidebar request cannot escape the selected range.

VALID (fixed): #1 -- restore Sessions dates before loading a direct detail route.

Author: wesm

frontend/e2e/session-list.spec.ts

@@ -106,4 +106,38 @@ test.describe("Session list", () => {
     expect(requestUrl.searchParams.get("date_from")).toBe(expectedFrom);
     expect(requestUrl.searchParams.get("date_to")).toBe(expectedTo);
   });
+
+  test("linked dates reach the first request on direct detail entry", async ({
+    page,
+  }) => {
+    const sessionId = await sp.sessionItems.first().getAttribute(
+      "data-session-id",
+    );
+    expect(sessionId).toBeTruthy();
+
+    await page.locator(".kit-date-range-picker__trigger").click();
+    await page.getByRole("button", { name: "90d", exact: true }).click();
+    await expect(page).toHaveURL(/window_days=90/);
+    const selectedUrl = new URL(page.url());
+    const expectedFrom = selectedUrl.searchParams.get("date_from");
+    const expectedTo = selectedUrl.searchParams.get("date_to");
+
+    await page.getByRole("button", { name: "Settings" }).click();
+    await page
+      .getByRole("checkbox", { name: "Link date ranges across pages" })
+      .check();
+
+    const requestPromise = page.waitForRequest((request) =>
+      new URL(request.url()).pathname.endsWith(
+        "/api/v1/sessions/sidebar-index",
+      )
+    );
+    await page.goto(`/sessions/${encodeURIComponent(sessionId!)}`);
+    const requestUrl = new URL((await requestPromise).url());
+
+    expect(requestUrl.searchParams.get("date_from")).toBe(expectedFrom);
+    expect(requestUrl.searchParams.get("date_to")).toBe(expectedTo);
+    await expect(page).toHaveURL(/date_from=/);
+    await expect(page).toHaveURL(/date_to=/);
+  });
 });

frontend/src/App.svelte

@@ -344,10 +344,14 @@
     untrack(() => {
       previousDateRestoreRoute = route;
       const sid = router.sessionId;
-      if (!sid && route === "sessions" && hasFilterParams(params)) {
+      if (
+        route === "sessions" &&
+        hasFilterParams(params) &&
+        (!sid || enteringSessions)
+      ) {
         sessions.initFromParams(params);
       }
-      if (!sid && enteringSessions) {
+      if (enteringSessions) {
         const entryParams = sessionEntryDateParams(params);
         if (entryParams) router.replaceParams(entryParams);
       }

frontend/src/App.test.ts

@@ -292,6 +292,71 @@ describe("findUserPromptOrdinal", () => {
 });
 
 describe("App analytics date navigation", () => {
+  it("applies an enabled shared range when entering session detail", async () => {
+    const sessionLoadDates: Array<{
+      dateFrom: string;
+      dateTo: string;
+    }> = [];
+    vi.stubGlobal(
+      "ResizeObserver",
+      class {
+        observe() {}
+        unobserve() {}
+        disconnect() {}
+      },
+    );
+    vi.spyOn(settings, "load").mockResolvedValue();
+    vi.spyOn(starred, "load").mockResolvedValue();
+    vi.spyOn(sync, "loadStatus").mockResolvedValue();
+    vi.spyOn(sync, "loadStats").mockResolvedValue();
+    vi.spyOn(sync, "loadVersion").mockResolvedValue();
+    vi.spyOn(sync, "checkForUpdate").mockResolvedValue();
+    vi.spyOn(sync, "startPolling").mockImplementation(() => {});
+    vi.spyOn(sync, "watchSession").mockImplementation(() => {});
+    vi.spyOn(sessions, "load").mockImplementation(() => {
+      sessionLoadDates.push({
+        dateFrom: sessions.filters.dateFrom,
+        dateTo: sessions.filters.dateTo,
+      });
+      return Promise.resolve();
+    });
+    vi.spyOn(sessions, "loadProjects").mockResolvedValue();
+    vi.spyOn(sessions, "loadAgents").mockResolvedValue();
+    vi.spyOn(sessions, "attachSidebar").mockReturnValue(() => {});
+    vi.spyOn(sessions, "navigateToSession").mockImplementation(async (id) => {
+      sessions.activeSessionId = id;
+    });
+    vi.spyOn(analytics, "fetchAll").mockResolvedValue();
+    vi.spyOn(analytics, "fetchSignalsForInsights").mockResolvedValue();
+    vi.spyOn(insights, "load").mockResolvedValue();
+
+    window.history.replaceState(null, "", "/insights");
+    router.route = "insights";
+    router.params = {};
+    router.sessionId = null;
+    yokedDates.setEnabled(true);
+    yokedDates.updateFromPanel({
+      from: "2026-05-01",
+      to: "2026-05-31",
+      mode: "fixed",
+    });
+
+    component = mount(App, { target: document.body });
+    await flushEffects();
+    sessionLoadDates.length = 0;
+
+    router.navigateToSession("session-1");
+    await flushEffects();
+
+    expect(sessionLoadDates[0]).toEqual({
+      dateFrom: "2026-05-01",
+      dateTo: "2026-05-31",
+    });
+    expect(router.sessionId).toBe("session-1");
+    expect(router.params.date_from).toBe("2026-05-01");
+    expect(router.params.date_to).toBe("2026-05-31");
+  });
+
   it("applies an enabled shared range to the first Sessions load", async () => {
     const sessionLoadFilters: Array<{
       project: string;