Implement fast userspace multihop mesh routing

Replace the one-intermediate-peer relay with protocol-scoped connectivity
graphs and precomputed shortest-path/ECMP forwarding snapshots. Independent
transport readers forward opaque transit frames without a plugin or TUN
round trip. Carry source, destination, a bounded hop limit and stable flow
tags; preserve end-to-end WireGuard links across topology changes.

Classify IP flows before encryption and preserve their tags through the
WireGuard pending queue. Add offline four-agent path-change coverage, loop
and isolation tests, and an opt-in release forwarding microbenchmark. Bump
control/data ALPNs while preserving persistent network identities and state.

Also include the pending Windows Mainline idle-timeout fix and its regression
test, using a reproducible vendored dependency patch.

Validation: fmt, workspace Clippy with warnings denied, and 307 release tests
passed. Two pre-existing Windows SQLite wipe failures were excluded; public
DHT and the manual benchmark remain ignored by default. The forwarding
microbenchmark measured 103 ns (64 B) and 202 ns (1280 B) per transit packet,
excluding encryption and socket I/O.

vendor/mainline/Cargo.toml

@@ -0,0 +1,147 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2021"
+rust-version = "1.85"
+name = "mainline"
+version = "8.0.0"
+authors = [
+    "nuh.dev",
+    "SeverinAlexB <severin@synonym.to>",
+    "SHAcollision <shacollision@synonym.to>",
+    "dzdidi <denys@synonym.to>",
+    "Kevin Karsopawiro <kevin@synonym.to>",
+]
+build = false
+exclude = [
+    "/docs/*",
+    "/examples/*",
+]
+autolib = false
+autobins = false
+autoexamples = false
+autotests = false
+autobenches = false
+description = "Simple, robust, BitTorrent's Mainline DHT implementation"
+homepage = "https://github.com/pubky/mainline"
+readme = "README.md"
+keywords = [
+    "bittorrent",
+    "torrent",
+    "dht",
+    "kademlia",
+    "mainline",
+]
+categories = ["network-programming"]
+license = "MIT"
+repository = "https://github.com/pubky/mainline"
+
+[package.metadata.docs.rs]
+all-features = true
+
+[features]
+async = [
+    "node",
+    "flume/async",
+    "dep:futures-lite",
+]
+default = ["full"]
+full = ["async"]
+node = ["dep:flume"]
+
+[lib]
+name = "mainline"
+path = "src/lib.rs"
+
+[dependencies.crc]
+version = "3.4.0"
+default-features = false
+
+[dependencies.document-features]
+version = "0.2.12"
+
+[dependencies.dyn-clone]
+version = "1.0.20"
+default-features = false
+
+[dependencies.ed25519-dalek]
+version = "3.0.0-pre.1"
+default-features = false
+
+[dependencies.flume]
+version = "0.12.0"
+optional = true
+default-features = false
+
+[dependencies.futures-lite]
+version = "2.6.1"
+optional = true
+default-features = false
+
+[dependencies.getrandom]
+version = "0.4"
+default-features = false
+
+[dependencies.lru]
+version = "0.16.2"
+default-features = false
+
+[dependencies.serde]
+version = "1.0.228"
+features = ["derive"]
+
+[dependencies.serde_bencode]
+version = "0.2.4"
+default-features = false
+
+[dependencies.serde_bytes]
+version = "0.11.19"
+
+[dependencies.sha1_smol]
+version = "1.0.1"
+default-features = false
+
+[dependencies.thiserror]
+version = "2.0.18"
+default-features = false
+
+[dependencies.tracing]
+version = "0.1.44"
+
+[dev-dependencies.clap]
+version = "4.5.57"
+features = ["derive"]
+
+[dev-dependencies.colored]
+version = "3.1.1"
+
+[dev-dependencies.ctrlc]
+version = "3.5.1"
+
+[dev-dependencies.dashmap]
+version = "6.1"
+
+[dev-dependencies.flume]
+version = "0.12.0"
+default-features = false
+
+[dev-dependencies.futures]
+version = "0.3.31"
+
+[dev-dependencies.histo]
+version = "1.0.0"
+
+[dev-dependencies.rayon]
+version = "1.11.0"
+
+[dev-dependencies.tracing-subscriber]
+version = "0.3"