chore: rename project quicnprotochat -> quicproquo (binaries: qpq)

Rename the entire workspace:
- Crate packages: quicnprotochat-{core,proto,server,client,gui,p2p,mobile} -> quicproquo-*
- Binary names: quicnprotochat -> qpq, quicnprotochat-server -> qpq-server,
  quicnprotochat-gui -> qpq-gui
- Default files: *-state.bin -> qpq-state.bin, *-server.toml -> qpq-server.toml,
  *.db -> qpq.db
- Environment variable prefix: QUICNPROTOCHAT_* -> QPQ_*
- App identifier: chat.quicnproto.gui -> chat.quicproquo.gui
- Proto package: quicnprotochat.bench -> quicproquo.bench
- All documentation, Docker, CI, and script references updated

HKDF domain-separation strings and P2P ALPN remain unchanged for
backward compatibility with existing encrypted state and wire protocol.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/quicproquo-proto/build.rs

@@ -0,0 +1,59 @@
+//! Build script for quicproquo-proto.
+//!
+//! Invokes the `capnp` compiler to generate Rust types from `.capnp` schemas
+//! located in the workspace-root `schemas/` directory.
+//!
+//! # Prerequisites
+//!
+//! The `capnp` CLI must be installed and on `PATH`.
+//!
+//! Debian/Ubuntu:  apt-get install capnproto
+//! macOS:          brew install capnp
+//! Docker:         see docker/Dockerfile
+
+use std::{env, path::PathBuf};
+
+fn main() {
+    let manifest_dir =
+        PathBuf::from(env::var("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR not set by Cargo"));
+
+    // Workspace root is two levels above this crate (quicproquo/crates/quicproquo-proto).
+    let workspace_root = manifest_dir
+        .join("../..")
+        .canonicalize()
+        .expect("could not canonicalize workspace root path");
+
+    let schemas_dir = workspace_root.join("schemas");
+
+    // Re-run this build script whenever any schema file changes.
+    println!(
+        "cargo:rerun-if-changed={}",
+        schemas_dir.join("auth.capnp").display()
+    );
+    println!(
+        "cargo:rerun-if-changed={}",
+        schemas_dir.join("delivery.capnp").display()
+    );
+    println!(
+        "cargo:rerun-if-changed={}",
+        schemas_dir.join("node.capnp").display()
+    );
+    println!(
+        "cargo:rerun-if-changed={}",
+        schemas_dir.join("federation.capnp").display()
+    );
+
+    capnpc::CompilerCommand::new()
+        // Treat `schemas/` as the include root so that inter-schema imports
+        // resolve correctly.
+        .src_prefix(&schemas_dir)
+        .file(schemas_dir.join("auth.capnp"))
+        .file(schemas_dir.join("delivery.capnp"))
+        .file(schemas_dir.join("node.capnp"))
+        .file(schemas_dir.join("federation.capnp"))
+        .run()
+        .expect(
+            "Cap'n Proto schema compilation failed. \
+             Is `capnp` installed? (apt-get install capnproto / brew install capnp)",
+        );
+}