greenfield: clean slate for ALPN-as-service pivot

Delete old source crates (alknet-core, alknet, alknet-napi), old
architecture docs (ADRs, specs, open questions), old research docs
(phase2, event-sourcing, feasibility, etc.), old tasks, and obsolete
reference material (gitserver/MPL, honker, nats, rustfs, polyglot,
keystone, distributed-identity).

Keep: alknet-secret (standalone, compiles), pivot docs, iroh and ssh
references, rudolfs reference (MIT/Apache, fork candidate), ops docs,
sdd_process.md, and licenses.

Previous implementation preserved at /workspace/@alkdev/alknet-main/
for reference during porting.

Workspace compiles: cargo check + 14 tests pass for alknet-secret.

crates/alknet-core/Cargo.toml

@@ -1,56 +0,0 @@
-[package]
-name = "alknet-core"
-version.workspace = true
-edition.workspace = true
-license.workspace = true
-description = "Core library for Alknet: pluggable SSH tunnel transport, SOCKS5 proxy, port forwarding, and authentication"
-repository.workspace = true
-
-[lib]
-name = "alknet_core"
-
-[features]
-default = []
-tls = ["dep:tokio-rustls", "dep:rustls", "dep:rustls-pki-types", "dep:webpki-roots"]
-iroh = ["dep:iroh", "dep:url"]
-acme = ["dep:rustls-acme", "dep:futures", "tls"]
-http = ["dep:axum", "dep:hyper", "dep:hyper-util", "dep:tower", "dep:http-body-util"]
-irpc = []
-testutil = []
-transport-traits = []
-
-[dependencies]
-russh = "0.49"
-tokio = { version = "1", features = ["full"] }
-tracing = "0.1"
-anyhow = "1"
-thiserror = "2"
-tokio-util = { version = "0.7", features = ["compat"] }
-tokio-rustls = { version = "0.26", optional = true }
-rustls = { version = "0.23", optional = true, features = ["aws_lc_rs"] }
-rustls-pki-types = { version = "1", optional = true }
-rustls-acme = { version = "0.12", optional = true }
-futures = { version = "0.3", optional = true }
-webpki-roots = { version = "0.26", optional = true }
-iroh = { version = "0.34", optional = true }
-url = { version = "2", optional = true }
-async-trait = "0.1"
-ipnetwork = "0.21.1"
-arc-swap = "1"
-serde = { version = "1", features = ["derive"] }
-serde_json = "1"
-sha2 = "0.10"
-hex = "0.4"
-axum = { version = "0.8", optional = true }
-hyper = { version = "1", optional = true }
-hyper-util = { version = "0.1", features = ["tokio", "server", "service"], optional = true }
-tower = { version = "0.5", optional = true }
-http-body-util = { version = "0.1", optional = true }
-
-[dev-dependencies]
-alknet-core = { path = ".", features = ["testutil", "tls", "iroh", "http"] }
-tempfile = "3"
-rcgen = "0.14"
-rand_core = "0.6"
-ssh-key = { version = "0.6", features = ["ed25519", "alloc"] }
-rand = "0.10.1"