fix(nests): wrapper.announces() ALSO needs channelFlow (collectLatest emits cross-coroutine)

The channelFlow conversion in f17e7ad fixed `MoqLiteNestsListener.announces`
but the SAME `IllegalStateException: Flow invariant is violated` kept
firing in the next two-phone repro (commit f17e7ad, run 15:46:51) — this
time the offending `flow{}` was one layer up, in
`ReconnectingNestsListener.announces`:

  override fun announces(): Flow<RoomAnnouncement> =
      flow {
          activeListener.collectLatest { listener ->
              ...
              runCatching {
                  listener.announces().collect { emit(it) }  // <-- HERE
              }
          }
      }

`Flow.collectLatest { lambda }` cancels and restarts a CHILD coroutine
for each upstream emission. The lambda body runs in that child, NOT in
the surrounding flow{} body's coroutine. So when the lambda invokes
`emit(it)`, it's emitting from a child coroutine. `flow{}`'s
SafeFlow guard rejects this with the same "Emission from another
coroutine is detected" error the inner listener was throwing before
my last fix.

Net effect on the user's repro: the inner channelFlow now correctly
sends RoomAnnouncement to the wrapper's `listener.announces().collect`
lambda, but that lambda's `emit(it)` to the wrapper's flow{} body
fails the same SafeFlow check, the wrapper's runCatching swallows the
exception (as `iter=2 inner collect ended IllegalStateException ...
fwd=1`), `_announcedSpeakers` stays empty, cliff detector never fires.

Fix: convert `ReconnectingNestsListener.announces` from `flow{} + emit`
to `channelFlow{} + send`, matching the inner listener's shape. The
combination of `channelFlow + collectLatest + send` is the canonical
pattern in kotlinx-coroutines for "switch-map" semantics with cross-
coroutine production. `awaitClose { }` is empty because `collectLatest`
on an infinite-StateFlow never completes naturally — cancellation
propagates through structured concurrency when the consumer cancels
the channelFlow.

Tests: every nestsClient + commons unit test still passes, including
the 12 CliffDetectorTest cases pinning the predicate's behaviour.

Together with f17e7ad (inner channelFlow), this should finally close
the chain: inner emits RoomAnnouncement on its channelFlow → wrapper's
collectLatest receives it inside its child coroutine → wrapper's
channelFlow.send forwards across the channel → consumer's
observeAnnounces collect receives → `_announcedSpeakers` populates →
cliff detector tick reports `announced=1` → on a real cliff event the
recycle fires.

nestsClient/src/commonMain/kotlin/com/vitorpamplona/nestsclient/ReconnectingNestsListener.kt

@@ -29,6 +29,7 @@ import com.vitorpamplona.quartz.utils.Log
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Job
 import kotlinx.coroutines.channels.BufferOverflow
+import kotlinx.coroutines.channels.awaitClose
 import kotlinx.coroutines.currentCoroutineContext
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.Flow
@@ -37,9 +38,9 @@ import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asSharedFlow
 import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.channelFlow
 import kotlinx.coroutines.flow.collectLatest
 import kotlinx.coroutines.flow.first
-import kotlinx.coroutines.flow.flow
 import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
@@ -251,8 +252,25 @@ private class ReconnectingHandle(
      * swallowed so a future moq-lite session keeps emitting.
      */
     override fun announces(): Flow<RoomAnnouncement> =
-        flow {
-            Log.d("NestRx") { "wrapper.announces() flow starting collect on activeListener" }
+        // `channelFlow` (NOT `flow`) is required here for the same
+        // reason `MoqLiteNestsListener.announces` is channelFlow:
+        // we drive emissions from a `collectLatest` that internally
+        // launches a child coroutine per `activeListener` emission.
+        // `flow {}`'s SafeFlow guard rejects emissions from any
+        // coroutine other than the flow-builder's own — so on the
+        // very first listener emission the inner `emit(it)` lands
+        // in a child coroutine of `collectLatest`, throws
+        // IllegalStateException, the consumer's `runCatching`
+        // swallows it, and `_announcedSpeakers` never populates.
+        // Two-phone production logs at commit f17e7ad showed this
+        // exact failure even AFTER the inner listener was switched
+        // to channelFlow — the wrapper layer was the second
+        // un-fixed `flow {}`. `channelFlow` + `send(...)` instead
+        // of `emit(...)` allows cross-coroutine production, which
+        // is exactly what `collectLatest`'s per-emission child
+        // coroutines need.
+        channelFlow {
+            Log.d("NestRx") { "wrapper.announces() channelFlow starting collect on activeListener" }
             var iter = 0
             activeListener.collectLatest { listener ->
                 iter += 1
@@ -271,7 +289,7 @@ private class ReconnectingHandle(
                     runCatching {
                         listener.announces().collect {
                             fwd += 1
-                            emit(it)
+                            send(it)
                         }
                     }
                 Log.w("NestRx") {
@@ -279,6 +297,12 @@ private class ReconnectingHandle(
                     "wrapper.announces() iter=$iter inner collect ended $why fwd=$fwd"
                 }
             }
+            // collectLatest above never returns naturally — it
+            // collects activeListener forever. awaitClose fires when
+            // the consumer cancels the channelFlow, at which point
+            // the collectLatest is cancelled too via structured
+            // concurrency.
+            awaitClose { }
         }
 
     /**