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>

bitchatTests/BLEServiceCoreTests.swift

@@ -216,6 +216,69 @@ struct BLEServiceCoreTests {
             cachedServiceUUIDs: [BLEService.serviceUUID, otherService]
         ))
     }
+
+    /// Pings are unsigned, so their claimed sender is attacker-controlled.
+    /// The pong budget must be keyed on the ingress link (the directly
+    /// connected peer that delivered the packet): rotating forged sender IDs
+    /// over one link exhausts one budget instead of resetting it, so a single
+    /// malicious link cannot turn /ping into an amplification primitive.
+    @Test
+    func meshPingResponseBudget_isPerIngressLinkNotClaimedSender() async throws {
+        let ble = makeService()
+        let outbound = OutboundPacketTap()
+        ble._test_onOutboundPacket = outbound.record
+
+        let link = PeerID(str: "1122334455667788")
+        let budget = TransportConfig.meshPingInboundMaxPerLink
+        let myRecipientData = try #require(Data(hexString: ble.myPeerID.id))
+
+        for i in 0..<(budget * 2) {
+            // A fresh forged sender for every ping, all arriving on one link.
+            let forgedSender = PeerID(str: String(format: "%016x", 0xA0_0000 + i))
+            var nonce = Data(repeating: 0, count: MeshPingPayload.nonceLength)
+            nonce[0] = UInt8(i)
+            let payload = try #require(MeshPingPayload(nonce: nonce, originTTL: 7))
+            let packet = BitchatPacket(
+                type: MessageType.ping.rawValue,
+                senderID: Data(hexString: forgedSender.id) ?? Data(),
+                recipientID: myRecipientData,
+                timestamp: UInt64(Date().timeIntervalSince1970 * 1000),
+                payload: payload.encode(),
+                signature: nil,
+                ttl: 7
+            )
+            ble._test_handlePacket(packet, fromPeerID: link, preseedPeer: false)
+        }
+
+        let reachedBudget = await TestHelpers.waitUntil(
+            { outbound.count(ofType: .pong) >= budget },
+            timeout: TestConstants.defaultTimeout
+        )
+        #expect(reachedBudget)
+        // Give any over-budget pong a chance to surface, then confirm the
+        // rotated sender IDs never bought a sixth response.
+        let exceededBudget = await TestHelpers.waitUntil(
+            { outbound.count(ofType: .pong) > budget },
+            timeout: TestConstants.shortTimeout
+        )
+        #expect(!exceededBudget)
+        #expect(outbound.count(ofType: .pong) == budget)
+    }
+}
+
+/// Thread-safe capture of packets leaving the service under test.
+private final class OutboundPacketTap {
+    private let lock = NSLock()
+    private var packets: [BitchatPacket] = []
+
+    func record(_ packet: BitchatPacket) {
+        lock.lock(); packets.append(packet); lock.unlock()
+    }
+
+    func count(ofType type: MessageType) -> Int {
+        lock.lock(); defer { lock.unlock() }
+        return packets.filter { $0.type == type.rawValue }.count
+    }
 }
 
 private func makeService() -> BLEService {