feat(edit): event editing — shared form, scoped recurring writes, recurrence picker (v1.3)

The create form (v1.2) now edits: a pencil on the detail screen (writable
calendars only, contextual WRITE upgrade like delete) opens it prefilled via
EventDetail.toEditForm; populated sections always show, the calendar is
fixed, and a dirty-check writes only changed columns (pristine saves are
no-ops). Saving a dirty recurring event parks in SaveUiState.AwaitingScope
and asks how far the change reaches (Google model): "only this event" =
modified-occurrence exception via CONTENT_EXCEPTION_URI (empty optionals as
explicit NULLs since the provider clones the parent row), "this and all
following" = series split (insert new event first, then truncate), "all
events" = series-row update with the time delta applied to the series
DTSTART. A changed rule drops the exception option. Delete gained the same
middle scope.

Recurrence: EventForm.rrule + SimpleRecurrence (FREQ/INTERVAL/UNTIL/COUNT +
weekly BYDAY with locale-ordered weekday toggles) behind a picker on create
and edit; unrepresentable rules render humanized (shared ui/common
RecurrenceText) and survive verbatim. UNTIL validation flags rules ending
before the event starts.

Provider lessons baked in (verified on-device via adb probes): instance
caches regenerate only from an update's own values, so truncation sends the
full time-column set (truncateSeries) — RRULE-only updates left a stale
duplicate occurrence on the split day; UNTIL is written as the local end of
day in UTC (toRRule(zone), previousLocalDayEndUtcMillis) so UTC+x zones
can't leak an extra day. Reminder edits reconcile against actual provider
rows, keeping untouched rows' methods.

Tests: RecurrenceTest (parse/render/round-trip, truncation), update/exception
mapper paths, repository pass-throughs, prefill + populatedFields, raw-title
mapper.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/src/main/java/de/jeanlucmakiola/calendula/ui/CalendarHost.kt

@@ -76,6 +76,15 @@ fun CalendarHost(modifier: Modifier = Modifier) {
         createDateIso = date.toString()
     }
 
+    // Edit form (v1.3) — reuses the detail screen's occurrence key; for
+    // recurring events the form itself asks for the write scope at save
+    // time. A saved edit closes the detail screen too: the occurrence the
+    // user tapped may not exist anymore (time moved, recurrence changed), so
+    // falling back to the auto-refreshing calendar is the only honest
+    // destination.
+    var editKey by rememberSaveable { mutableStateOf<LongArray?>(null) }
+    var heldEditKey by remember { mutableStateOf<LongArray?>(null) }
+
     val slideSpec = rememberCalendarSlideSpec()
 
     Box(modifier = modifier.fillMaxSize()) {
@@ -117,6 +126,10 @@ fun CalendarHost(modifier: Modifier = Modifier) {
                     beginMillis = key[1],
                     endMillis = key[2],
                     onBack = { detailKey = null },
+                    onEdit = {
+                        heldEditKey = key
+                        editKey = key
+                    },
                 )
             }
         }
@@ -131,6 +144,26 @@ fun CalendarHost(modifier: Modifier = Modifier) {
                 EventEditScreen(
                     initialDateIso = iso,
                     onClose = { createDateIso = null },
+                    onSaved = { createDateIso = null },
+                )
+            }
+        }
+
+        // Edit form (v1.3) — slides over the detail screen.
+        AnimatedVisibility(
+            visible = editKey != null,
+            enter = slideInHorizontally(slideSpec) { it } + fadeIn(),
+            exit = slideOutHorizontally(slideSpec) { it } + fadeOut(),
+        ) {
+            (editKey ?: heldEditKey)?.let { key ->
+                EventEditScreen(
+                    initialDateIso = null,
+                    editKey = key,
+                    onClose = { editKey = null },
+                    onSaved = {
+                        editKey = null
+                        detailKey = null
+                    },
                 )
             }
         }