revert(sheets): take out Back closing the open sheet

Opening a sheet pushed a history entry, and closing it took that entry
off again with a history back. The browser answers that back later, so
when the close started a navigation it landed after the router's push
and undid it: the medication wizard stayed on the list instead of
opening the new medication, a section picked from the settings list on
a phone stayed on the account page, and a link followed from a sheet
could put the page under it back.

The sheet history goes, with its wiring in ResponsiveSheet, the
document sheet's opt-out, the account form's deference to it, Back
answering the discard question, and their tests. Back behaves as
before: it leaves the page and the sheet goes with it, and the account
form's own Back guard answers every Back again. A tap outside, Escape,
the X and a swipe still ask before dropping typed input. The two size
baselines return to their earlier numbers.

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": 335,
-  "total": 109080,
+  "total": 109077,
   "entries": {
     "app/achievements/page.tsx :: AchievementsPage": 206,
     "app/api/admin/backups/upload/route.ts :: apiHandler(arg)": 275,
@@ -90,7 +90,7 @@
     "components/documents/document-ai-section.tsx :: DocumentAiSection": 262,
     "components/documents/document-bulk-bar.tsx :: DocumentBulkBar": 204,
     "components/documents/document-card.tsx :: DocumentCard": 354,
-    "components/documents/document-detail-sheet.tsx :: DocumentDetailSheet": 327,
+    "components/documents/document-detail-sheet.tsx :: DocumentDetailSheet": 325,
     "components/documents/document-facts-review.tsx :: DocumentFactsSection": 242,
     "components/documents/document-facts-review.tsx :: FactRow": 261,
     "components/documents/document-filter-bar.tsx :: DocumentFilterBar": 348,
@@ -225,7 +225,7 @@
     "components/timeline/timeline-chart.tsx :: ChartBody": 236,
     "components/timeline/timeline-chronicle.tsx :: TimelineChronicle": 246,
     "components/timeline/timeline-view.tsx :: TimelineView": 478,
-    "components/ui/responsive-sheet.tsx :: ResponsiveSheet": 255,
+    "components/ui/responsive-sheet.tsx :: ResponsiveSheet": 253,
     "components/vaccinations/catalog-picker.tsx :: CatalogPicker": 221,
     "components/vaccinations/custom-vaccine-sheet.tsx :: CustomVaccineSheet": 246,
     "components/vaccinations/vaccination-form.tsx :: VaccinationForm": 218,