fix(sheets): let Back close the open sheet

Back on a phone (the Android button, the edge swipe of the installed
app) with a sheet open went back a page under it: the sheet and what
was typed in it were gone, in the edit sheets too. Only the account
form guarded Back, behind an option.

Opening a ResponsiveSheet now pushes one history entry with the page's
URL. Back lands below it and closes the sheet, asking first when it
holds unsaved input or when its owner keeps it open; a sheet closed any
other way takes its entry off again, so the next Back still leaves the
page. A history write made while that Back is under way waits for it, a
link followed from a sheet replaces the sheet's entry, and the page
entry keeps the URL the page has now, so a stripped one-shot `?add=`
does not come back. The vault's document sheet already owns `?doc=` and
opts out.

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

@@ -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": 325,
+    "components/documents/document-detail-sheet.tsx :: DocumentDetailSheet": 327,
     "components/documents/document-facts-review.tsx :: DocumentFactsSection": 242,
     "components/documents/document-facts-review.tsx :: FactRow": 261,
     "components/documents/document-filter-bar.tsx :: DocumentFilterBar": 348,
@@ -229,7 +229,7 @@
     "components/timeline/timeline-chart.tsx :: ChartBody": 236,
     "components/timeline/timeline-chronicle.tsx :: TimelineChronicle": 246,
     "components/timeline/timeline-view.tsx :: TimelineView": 486,
-    "components/ui/responsive-sheet.tsx :: ResponsiveSheet": 253,
+    "components/ui/responsive-sheet.tsx :: ResponsiveSheet": 255,
     "components/vaccinations/catalog-picker.tsx :: CatalogPicker": 221,
     "components/vaccinations/custom-vaccine-sheet.tsx :: CustomVaccineSheet": 246,
     "components/vaccinations/vaccination-form.tsx :: VaccinationForm": 218,

src/__tests__/url-state-writes-guard.test.ts

@@ -24,6 +24,8 @@ const ALLOWED: Record<string, string> = {
   "lib/url-state.ts": "the helper itself",
   "components/clinician/share-unlock-gate.tsx":
     "scrubs a passphrase from the fragment synchronously, before the unlock request leaves; no query state",
+  "components/ui/sheet-history.ts":
+    "a sheet's own history entry: the page's URL unchanged, never query state",
   "components/documents/vault/selection-history.ts":
     "closeDocumentSelectionHistoryEntry takes a history-shaped argument for its tests; the page passes `urlStateHistory`",
 };