fix(sheets): put a swiped sheet back when it asks before closing

A swipe past the close point paints the sheet where the finger let go and
asks the owner to close it. A sheet holding unsaved input asks about
discarding first and stays open, so it sat half pushed off the screen
behind the question. One frame after the close, a sheet whose content is
still open now glides back to its resting place. The function's size
baseline rises by the seven lines this takes.

src/__tests__/baselines/source-function-lines.json

@@ -1,7 +1,7 @@
 {
   "$comment": "Production functions over 200 lines, keyed \"file :: name\", and their length. Maintained by src/__tests__/source-size-ratchet.test.ts.",
   "count": 336,
-  "total": 109378,
+  "total": 109385,
   "entries": {
     "app/achievements/page.tsx :: AchievementsPage": 206,
     "app/api/admin/backups/upload/route.ts :: apiHandler(arg)": 275,
@@ -231,7 +231,7 @@
     "components/vaccinations/custom-vaccine-sheet.tsx :: CustomVaccineSheet": 246,
     "components/vaccinations/vaccination-form.tsx :: VaccinationForm": 218,
     "components/workouts/manual-workout-form.tsx :: ManualWorkoutForm": 321,
-    "hooks/use-sheet-drag.ts :: createSheetDrag": 312,
+    "hooks/use-sheet-drag.ts :: createSheetDrag": 319,
     "lib/activity/calendar-math.ts :: buildActivityCalendar": 204,
     "lib/ai/anthropic-client.ts :: generateCompletion": 294,
     "lib/ai/coach/cycle-snapshot.ts :: buildCycleSnapshotBlock": 202,

src/hooks/__tests__/use-sheet-drag.test.ts

@@ -23,6 +23,9 @@ interface FakeEl {
   parentElement: FakeEl | null;
   overflowY: string;
   own?: boolean;
+  /** Radix's `data-state` on the sheet content. */
+  state?: "open" | "closed";
+  getAttribute: (name: string) => string | null;
   closest: (selector: string) => FakeEl | null;
   getAnimations: () => Animation[];
   setPointerCapture: (id: number) => void;
@@ -39,6 +42,8 @@ function fake(partial: Partial<FakeEl> = {}): FakeEl {
     parentElement: null,
     overflowY: "visible",
     closest: () => (node.own ? node : null),
+    getAttribute: (name) =>
+      name === "data-state" ? (node.state ?? null) : null,
     getAnimations: () => [],
     setPointerCapture: vi.fn(),
     querySelector: () => null,
@@ -173,6 +178,29 @@ describe("createSheetDrag", () => {
     expect(s.controller.swallowClick()).toBe(false);
   });
 
+  it("returns to its rest when a guarded sheet stays open after the swipe", () => {
+    const s = setup();
+    // The owner asks about unsaved input instead of closing.
+    s.content.state = "open";
+    s.drag(s.header, 140, { stepMs: 40, restMs: 200 });
+    expect(s.onClose).toHaveBeenCalledTimes(1);
+    expect(s.content.style.transform).toBe("translate3d(0, 140px, 0)");
+
+    s.flushFrames();
+    expect(s.content.style.transform).toBe("translate3d(0, 0px, 0)");
+    expect(s.overlay.style.opacity).toBe("1");
+    s.timers.forEach((run) => run());
+    expect(s.content.style.transform).toBe("");
+  });
+
+  it("leaves a closing sheet where it was let go", () => {
+    const s = setup();
+    s.content.state = "closed";
+    s.drag(s.header, 140, { stepMs: 40, restMs: 200 });
+    s.flushFrames();
+    expect(s.content.style.transform).toBe("translate3d(0, 140px, 0)");
+  });
+
   it("lets its own close through: the swallowed click comes after it", () => {
     const s = setup();
     let swallowedDuringClose: boolean | null = null;

src/hooks/use-sheet-drag.ts

@@ -354,6 +354,13 @@ export function createSheetDrag(
         // Before the swallow is armed: the close is itself a click.
         options.onClose();
         swallow = true;
+        // A sheet holding unsaved input asks first and stays open meanwhile;
+        // put it back where it rests rather than where it was let go.
+        frame(() => {
+          if (options.content()?.getAttribute("data-state") === "open") {
+            settleTo(g, options.snap());
+          }
+        });
         return;
       }
       swallow = true;