Add mesh diagnostics: /ping, /trace, and topology map (#1377)

* Add mesh diagnostics: /ping, /trace, and topology map

- New protocol types ping=0x26 / pong=0x27 (9-byte payload: 8-byte nonce
  + origin TTL) with per-peer inbound rate limiting (5 per 10s)
- /ping @name reports RTT and hop count, 10s timeout
- /trace @name prints the estimated path from gossiped directNeighbors
- Topology map sheet (circular Canvas layout) reachable from App Info
- Ping/pong ride the deterministic directed-relay path like DMs
- Tests: payload round-trip, hop-count math, command output, edge
  normalization, layout

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

* 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>

* App Info: move NETWORK section under HOW TO USE and uppercase NETWORK/SYMBOLS headers

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

* Conform DiagnosticsMockContext to sendPublicMessage

CommandContextProvider gained sendPublicMessage (Cashu /pay, #1376) after
this branch forked, so the diagnostics test mock no longer conformed once
main was merged in. Add the no-op stub.

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

---------

Co-authored-by: jack <jackjackbits@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

bitchat/ViewModels/ChatViewModel.swift

@@ -1547,6 +1547,33 @@ final class ChatViewModel: ObservableObject, BitchatDelegate, TransportEventDele
         }
     }
 
+    /// Origin conversation for deferred command output, captured when the
+    /// command is issued (before any async work starts).
+    @MainActor
+    func currentCommandDestination() -> CommandOutputDestination {
+        if let peerID = selectedPrivateChatPeer {
+            return .privateChat(peerID)
+        }
+        // Deferring commands (/ping) are rejected in geohash channels, so a
+        // non-DM origin is always the #mesh timeline.
+        return .meshTimeline
+    }
+
+    /// Routes deferred command output (async /ping results) into the
+    /// conversation captured at issue time, immune to chat switches in the
+    /// meantime. A DM result lands in the origin chat's history even if that
+    /// chat is no longer selected (or was cleared — it then reappears as the
+    /// first message when the chat is reopened).
+    @MainActor
+    func addCommandOutput(_ content: String, to destination: CommandOutputDestination) {
+        switch destination {
+        case .privateChat(let peerID):
+            addLocalPrivateSystemMessage(content, to: peerID)
+        case .meshTimeline:
+            publicConversationCoordinator.addMeshOnlySystemMessage(content)
+        }
+    }
+
     // MARK: - Message Reception
 
     @MainActor