android: restore the dismiss I deleted, and teach the checker to see it

`785ebdb` failed at compileDebugKotlin with two `Unresolved reference 'dismiss'`.
Splitting the reminder notification code into its own object, I removed
`dismiss` from `Reminders` and never pasted it into `ReminderNotification`. The
call sites were correctly qualified; the function simply was not there.

All four local gates passed it, and `check-symbols.py` passed it for a reason it
documented about itself: it only resolved the LEADING segment of a dotted
expression, because that is the part a regex can resolve. `ReminderNotification`
existed, so `ReminderNotification.dismiss(...)` looked fine.

That was a real gap rather than an inherent one, so the checker now indexes the
members of every `object` declared in the package and verifies `Foo.bar` against
them. Brace-counted, not regex-matched — an object body is full of nested braces
from lambdas and apply blocks, and no regex closes correctly over them.

Verified by deleting `dismiss` from a copy of the tree again: it reports the
same two call sites the Kotlin compiler did. What it still cannot see is
narrowed and written down rather than left implied — members of anything
declared outside this package, members reached through a variable rather than a
type name, and every question about types.

android/app/src/main/java/com/fabledsword/thoughtsync/ReminderNotification.kt

@@ -78,6 +78,12 @@ internal object ReminderNotification {
         }
     }
 
+    /** Take a reminder off the shade, once it has been acted on. */
+    fun dismiss(
+        context: Context,
+        noteId: String,
+    ) = NotificationManagerCompat.from(context).cancel(noteId.hashCode())
+
     private fun openIntent(
         context: Context,
         note: Note,