Remove dead code found by full Periphery audit; add scan config + advisory CI (#1410)

Periphery 3.7.4 audit of both schemes (macOS + iOS, intersected so
platform-specific code is never touched), with test targets indexed and
the share extension built. 277 dead declarations removed or demoted:
dead forwarding wrappers (ChatViewModel+Nostr/+PrivateChat), removed-
feature remnants (autocomplete command suggestions, back-swipe tuning,
MediaSendError, GeohashParticipantTracker), unused Tor dormancy
bindings, assign-only properties, unused parameters (renamed to _), and
redundant public accessibility. 13 orphaned localization keys deleted
across all 29 locales (old pre-#1392 location-notes UI, app_info
warnings).

Two real tests were flagged as unused because they never ran: Swift
Testing methods missing @Test (NostrProtocolTests.
testAckRoundTripNIP44V2_Delivered, NotificationStreamAssemblerTests.
testAssemblesCompressedLargeFrame). Re-armed both; they pass.

Deliberately kept, now recorded in .periphery.baseline.json: iOS-only
code invisible to the CI macOS scan, C FFI signatures, keep-alive
NWPathMonitor reference, InboundEventKey.eventID (dedup semantics),
wifiBulk capability bit (reserved for Wi-Fi bulk work, used by
BitFoundation package tests), and the String secureClear cluster
(exercised by package tests).

New: .periphery.yml config and an advisory Dead Code CI job (mirrors
the SwiftLint precedent from #1361) that fails on findings not in the
committed baseline.

Verified: full macOS app suite, BitFoundation (119) and BitLogger (13)
package tests green; periphery scan --strict exits clean.

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

localPackages/BitFoundation/Sources/BitFoundation/BinaryProtocol.swift

@@ -105,10 +105,6 @@ public struct BinaryProtocol {
 
     // Field offsets within packet header
     public struct Offsets {
-        static let version = 0
-        static let type = 1
-        static let ttl = 2
-        static let timestamp = 3
         public static let flags = 11  // After version(1) + type(1) + ttl(1) + timestamp(8)
     }
 

localPackages/BitFoundation/Sources/BitFoundation/BitchatMessage.swift

@@ -341,21 +341,3 @@ extension BitchatMessage {
     }
 }
 
-extension Array where Element == BitchatMessage {
-    /// Filters out empty ones and deduplicate by ID while preserving order (from oldest to newest)
-    public func cleanedAndDeduped() -> [Element] {
-        let arr = filter { $0.content.trimmed.isEmpty == false }
-        guard arr.count > 1 else {
-            return arr
-        }
-        var seen = Set<String>()
-        var dedup: [BitchatMessage] = []
-        for m in arr.sorted(by: { $0.timestamp < $1.timestamp }) {
-            if !seen.contains(m.id) {
-                dedup.append(m)
-                seen.insert(m.id)
-            }
-        }
-        return dedup
-    }
-}

localPackages/BitFoundation/Sources/BitFoundation/BitchatPacket.swift

@@ -7,7 +7,6 @@
 //
 
 import struct Foundation.Data
-import struct Foundation.Date
 
 /// The core packet structure for all BitChat protocol messages.
 /// Encapsulates all data needed for routing through the mesh network,
@@ -37,35 +36,7 @@ public struct BitchatPacket: Codable {
         self.route = route
         self.isRSR = isRSR
     }
-    
-    // Convenience initializer for new binary format
-    init(type: UInt8, ttl: UInt8, senderID: PeerID, payload: Data, isRSR: Bool = false) {
-        self.version = 1
-        self.type = type
-        // Convert hex string peer ID to binary data (8 bytes)
-        var senderData = Data()
-        var tempID = senderID.id
-        while tempID.count >= 2 {
-            let hexByte = String(tempID.prefix(2))
-            if let byte = UInt8(hexByte, radix: 16) {
-                senderData.append(byte)
-            }
-            tempID = String(tempID.dropFirst(2))
-        }
-        self.senderID = senderData
-        self.recipientID = nil
-        self.timestamp = UInt64(Date().timeIntervalSince1970 * 1000) // milliseconds
-        self.payload = payload
-        self.signature = nil
-        self.ttl = ttl
-        self.route = nil
-        self.isRSR = isRSR
-    }
-    
-    var data: Data? {
-        BinaryProtocol.encode(self)
-    }
-    
+
     public func toBinaryData(padding: Bool = true) -> Data? {
         BinaryProtocol.encode(self, padding: padding)
     }