chore: rename quicproquo → quicprochat in Rust workspace

Rename all crate directories, package names, binary names, proto
package/module paths, ALPN strings, env var prefixes, config filenames,
mDNS service names, and plugin ABI symbols from quicproquo/qpq to
quicprochat/qpc.

crates/quicprochat-core/Cargo.toml

@@ -0,0 +1,88 @@
+[package]
+name        = "quicprochat-core"
+version     = "0.1.0"
+edition.workspace     = true
+description = "Crypto primitives, MLS state machine, and hybrid post-quantum KEM for quicprochat."
+license     = "Apache-2.0 OR MIT"
+repository.workspace  = true
+
+[features]
+default = ["native"]
+# The "native" feature enables MLS (openmls), OPAQUE, Cap'n Proto, tokio, and
+# filesystem-backed key storage. Disable it (--no-default-features) to compile
+# the pure-crypto subset to wasm32-unknown-unknown.
+native = [
+    "dep:openmls",
+    "dep:openmls_rust_crypto",
+    "dep:openmls_traits",
+    "dep:tls_codec",
+    "dep:opaque-ke",
+    "dep:bincode",
+    "dep:capnp",
+    "dep:quicprochat-proto",
+    "dep:tokio",
+]
+
+[dependencies]
+# Crypto — classical (always available, WASM-safe)
+x25519-dalek        = { workspace = true }
+ed25519-dalek       = { workspace = true }
+sha2                = { workspace = true }
+hmac                = { workspace = true }
+hkdf                = { workspace = true }
+ciborium            = { workspace = true }
+chacha20poly1305    = { workspace = true }
+zeroize             = { workspace = true }
+rand                = { workspace = true }
+serde               = { workspace = true }
+serde_json          = { workspace = true }
+argon2              = { workspace = true }
+thiserror           = { workspace = true }
+
+# Crypto — post-quantum hybrid KEM (M7) — always available, WASM-safe
+ml-kem              = { workspace = true }
+
+# Crypto — OPAQUE password-authenticated key exchange (native only)
+opaque-ke           = { workspace = true, optional = true }
+
+# Crypto — MLS (M2) (native only)
+openmls             = { workspace = true, optional = true }
+openmls_rust_crypto = { workspace = true, optional = true }
+openmls_traits      = { workspace = true, optional = true }
+tls_codec           = { workspace = true, optional = true }
+bincode             = { workspace = true, optional = true }
+
+# Serialisation (native only)
+capnp               = { workspace = true, optional = true }
+quicprochat-proto    = { path = "../quicprochat-proto", optional = true }
+
+# Async runtime (native only)
+tokio               = { workspace = true, optional = true }
+
+# WASM: provide getrandom with js backend
+[target.'cfg(target_arch = "wasm32")'.dependencies]
+getrandom           = { version = "0.2", features = ["js"] }
+
+[lints]
+workspace = true
+
+[dev-dependencies]
+tokio               = { workspace = true }
+criterion           = { version = "0.5", features = ["html_reports"] }
+prost               = "0.13"
+
+[[bench]]
+name = "serialization"
+harness = false
+
+[[bench]]
+name = "mls_operations"
+harness = false
+
+[[bench]]
+name = "hybrid_kem_bench"
+harness = false
+
+[[bench]]
+name = "crypto_benchmarks"
+harness = false