Fix CI media-wipe race, per-link ping rate limiting, and /ping output routing

Three fixes for PR #1377 review:

1. CI flake (sendImage_privateChatProcessesAndTransfersImage): the
   panicClearAllData / clearCurrentPublicTimeline detached utility-priority
   tasks delete the real ~/Library/Application Support/files tree, which the
   test process shares. The wipe fires at a nondeterministic time and raced
   the sendImage test's JPEG in files/images/outgoing (write then re-read),
   so prepareImagePacket threw and the test timed out. Both wipes are now
   skipped under tests (existing TestEnvironment.isRunningTests pattern);
   this also stops test runs from deleting the developer's real media.

2. Codex P1: ping packets are unsigned, so keying the pong rate limiter on
   packet.senderID let one connected peer rotate forged sender IDs to bypass
   the 5-per-10s budget. The limiter now keys on the ingress link (the
   directly connected peer that delivered the packet); the pong still goes
   to the claimed sender. Regression test proves rotating senders over one
   link exhaust one budget (fails 10 vs 5 pongs on the old code).

3. Codex P2: /ping output arrived up to 10s later and was routed from
   selectedPrivateChatPeer at callback time, misrouting the result after a
   chat switch. The origin conversation is now captured when the command is
   issued (CommandOutputDestination) and deferred output is routed there:
   a DM result lands in the origin chat's history even if deselected, and a
   mesh-timeline result pins to #mesh instead of the active channel.

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

bitchatTests/Services/MeshDiagnosticsTests.swift

@@ -129,6 +129,44 @@ struct MeshDiagnosticsTests {
         #expect(context.commandOutputs == ["no reply from alice"])
     }
 
+    @MainActor
+    @Test func pingOutputRoutesToConversationWhereCommandWasIssued() async {
+        let context = DiagnosticsMockContext()
+        let alice = PeerID(str: "abcd1234abcd1234")
+        let bob = PeerID(str: "b0b0b0b0b0b0b0b0")
+        context.nicknameToPeerID["alice"] = alice
+        let transport = MockTransport()
+        transport.meshPingResult = MeshPingResult(rttMs: 42, hops: 2)
+        let processor = makeProcessor(context: context, transport: transport)
+
+        // Issue the ping from bob's DM, then switch chats before the async
+        // result lands. The output must follow the origin conversation, not
+        // whatever is selected at callback time.
+        context.selectedPrivateChatPeer = bob
+        _ = processor.process("/ping @alice")
+        context.selectedPrivateChatPeer = nil
+
+        await waitForCommandOutput(context)
+        #expect(context.commandOutputDestinations == [.privateChat(bob)])
+    }
+
+    @MainActor
+    @Test func pingIssuedFromPublicTimelineRoutesToMeshTimeline() async {
+        let context = DiagnosticsMockContext()
+        let alice = PeerID(str: "abcd1234abcd1234")
+        context.nicknameToPeerID["alice"] = alice
+        let transport = MockTransport()
+        transport.meshPingResult = MeshPingResult(rttMs: 7, hops: 1)
+        let processor = makeProcessor(context: context, transport: transport)
+
+        _ = processor.process("/ping @alice")
+        // Opening a DM afterwards must not swallow the public-timeline result.
+        context.selectedPrivateChatPeer = alice
+
+        await waitForCommandOutput(context)
+        #expect(context.commandOutputDestinations == [.meshTimeline])
+    }
+
     // MARK: - /trace
 
     @MainActor
@@ -225,6 +263,7 @@ private final class DiagnosticsMockContext: CommandContextProvider {
 
     var nicknameToPeerID: [String: PeerID] = [:]
     private(set) var commandOutputs: [String] = []
+    private(set) var commandOutputDestinations: [CommandOutputDestination] = []
 
     func getPeerIDForNickname(_ nickname: String) -> PeerID? {
         nicknameToPeerID[nickname]
@@ -241,7 +280,15 @@ private final class DiagnosticsMockContext: CommandContextProvider {
     func addPublicSystemMessage(_ content: String) {}
     func toggleFavorite(peerID: PeerID) {}
 
-    func addCommandOutput(_ content: String) {
+    func currentCommandDestination() -> CommandOutputDestination {
+        if let peerID = selectedPrivateChatPeer {
+            return .privateChat(peerID)
+        }
+        return .meshTimeline
+    }
+
+    func addCommandOutput(_ content: String, to destination: CommandOutputDestination) {
         commandOutputs.append(content)
+        commandOutputDestinations.append(destination)
     }
 }