Add BLE L2CAP transport with scan-based auto-connect

BLE transport implementation using L2CAP Connection-Oriented Channels
(SeqPacket mode) via the bluer crate, behind cfg(feature = "ble").

Core transport:
- BleTransport<I> generic over BleIo trait (BluerIo prod, MockBleIo test)
- Connection pool with priority eviction (static > discovered, max 7)
- Connect-on-send via connect_inline() matching TCP behavior
- Per-connection receive loops with pool cleanup on disconnect

Discovery and probing:
- Combined scan_probe_loop using select! over scanner events and a
  BinaryHeap delay queue with per-entry random jitter (0-5s) to prevent
  herd effects when multiple nodes see the same beacon simultaneously
- Pre-handshake pubkey exchange ([0x00][pubkey:32]) for IK identity
- Cross-probe tie-breaker: smaller NodeAddr's outbound wins (same
  convention as FMP/FSP rekey dual-initiation)
- Probed peers reported to DiscoveryBuffer; pool fills through normal
  node-layer auto-connect -> send_async -> connect_inline path

Beacon management:
- Periodic advertising: 1s burst every 30s (configurable via
  beacon_interval_secs / beacon_duration_secs)
- FIPS service UUID for scan filtering

Configuration (all fields optional with defaults):
- adapter, psm, mtu, max_connections, connect_timeout_ms
- advertise, scan, auto_connect, accept_connections
- beacon_interval_secs (30), beacon_duration_secs (1)

Hardware validated with two BLE nodes:
- 2048-byte MTU, ~60-160ms RTT, zero-config auto-connect
- BLE spike tool at testing/ble/ for standalone adapter validation

42 unit tests + 4 node-level integration tests, all CI-compatible
via MockBleIo (no hardware required). tokio test-util added for
time-dependent scan/probe tests.

README.md

@@ -38,8 +38,8 @@ endpoints.
 
 - **Self-organizing mesh routing** — spanning tree coordinates with bloom
   filter guided discovery, no global routing tables
-- **Multi-transport** — UDP, TCP, Ethernet, and Tor today; designed for
-  Bluetooth, serial, and radio
+- **Multi-transport** — UDP, TCP, Ethernet, Tor, and Bluetooth (BLE L2CAP)
+  today; designed for serial and radio
 - **Noise encryption** — hop-by-hop link encryption (IK) plus independent
   end-to-end session encryption (XK), with periodic rekey for forward secrecy
 - **Nostr-native identity** — secp256k1 keypairs as node addresses, no
@@ -65,6 +65,10 @@ cargo build --release
 
 Requires Rust 1.85+ (edition 2024) and Linux with TUN support.
 
+The BLE transport (enabled by default) requires BlueZ and libdbus. On
+Debian/Ubuntu: `sudo apt install bluez libdbus-1-dev`. To build without BLE:
+`cargo build --release --no-default-features --features tui`.
+
 ## Installation
 
 After building, choose one of the following methods to install.
@@ -240,7 +244,7 @@ testing/      Docker-based integration test harnesses
 ## Status & Roadmap
 
 FIPS is at **v0.2.0**. The core protocol works end-to-end over UDP, TCP,
-Ethernet, and Tor with a small live mesh of deployed nodes.
+Ethernet, Tor, and Bluetooth (BLE) with a small live mesh of deployed nodes.
 
 ### What works today
 
@@ -253,7 +257,7 @@ Ethernet, and Tor with a small live mesh of deployed nodes.
 - Static hostname mapping (`/etc/fips/hosts`) with auto-reload
 - Per-link metrics (RTT, loss, jitter, goodput) and mesh size estimation
 - ECN congestion signaling (hop-by-hop CE relay, IPv6 CE marking, kernel drop detection)
-- UDP, TCP, Ethernet, and Tor transports (SOCKS5 outbound + directory-mode onion service inbound)
+- UDP, TCP, Ethernet, Tor, and BLE transports (BLE via L2CAP CoC with per-link MTU negotiation)
 - Runtime inspection and peer management via `fipsctl` and `fipstop`
 - Reproducible builds with toolchain pinning and SOURCE_DATE_EPOCH
 - Debian and systemd tarball packaging
@@ -263,7 +267,6 @@ Ethernet, and Tor with a small live mesh of deployed nodes.
 
 - Peer discovery via Nostr relays (bootstrap without static peer lists)
 - Native API for FIPS-aware applications (npub:port addressing)
-- Additional transports (Bluetooth)
 - Security audit of cryptographic protocols
 
 ### Longer-term