smc: _resolveAndEmit isClosed guard + honest 'session' stat label

Two Copilot fixes (+ a third pushback in the reply):

1. _resolveAndEmit awaits peerLookup. If the notifier is disposed
   during the await, _eventController.close() has already run; the
   subsequent _eventController.add would throw 'Bad state: Cannot
   add event after closing'. Added an isClosed check after the
   await before the identity check.

2. smc_stat_total_today msgstr read 'Total today' but the
   ShareState.totalCount is session-scoped (reset on every
   toggle-on, no day bucket, no persistence). Renamed to 'Total
   this session' so the label matches the implemented semantics.
   #8820's rebase later replaces this key with smc_stat_total_helped
   + 'Total people helped to date' alongside persistence via
   unboundedTotalHelped — until then the more honest 'session'
   wording matches reality.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: myleshorton

assets/locales/en.po

@@ -612,7 +612,7 @@ msgid "smc_stat_active_now"
 msgstr "Active now"
 
 msgid "smc_stat_total_today"
-msgstr "Total today"
+msgstr "Total this session"
 
 msgid "smc_connections_tooltip"
 msgstr "Most connections are short liveness probes — Lantern clients periodically check that this peer is reachable before sending real traffic. A quick burst from many locations is normal; an arc that lingers represents an actual user session."

lib/features/share_my_connection/share_my_connection.dart

@@ -486,6 +486,11 @@ class ShareNotifier extends Notifier<ShareState> {
     } catch (_) {
       geo = PeerGeo.unknown;
     }
+    // The notifier could have been disposed during the await (provider
+    // teardown closes _eventController). Guard before touching it so
+    // a late lookup completion doesn't throw "Bad state: Cannot add
+    // event after closing" on the disposed sink.
+    if (_eventController.isClosed) return;
     // Peer may have disconnected before the lookup returned. The map
     // entry's identity (workerIdx) is the cheapest check.
     final current = _peerArcs[ip];