fix(desktop): unblock native CI on windows and de-flake the idle heartbeat test

The locator HSM signer is a unix-socket daemon with no Windows target,
but its unconditional std::os::unix imports failed cargo check on the
windows runner — the socket server and secure-file layers are now
cfg(unix) with a stub main. The transfer-idle heartbeat test pinned its
handshake windows to the same 400ms as the deadline under test, so a
loaded runner could flake the connect phase; the idle deadline (and the
validation-capped handshake windows) now sit at 2s.

crates/op-collab-relay-locator-hsm/src/lib.rs

@@ -2,7 +2,12 @@ pub mod config;
 pub mod error;
 pub mod pkcs11;
 pub mod protocol;
+// The signer daemon speaks over a permission-checked Unix domain socket and
+// enforces unix file modes on its secrets; there is no Windows deployment
+// target, so the socket server and secure-file layers are unix-only.
+#[cfg(unix)]
 pub mod secure_file;
+#[cfg(unix)]
 pub mod server;
 
 pub use config::{KeyConfig, Region, SignerConfig};

crates/op-collab-relay-locator-hsm/src/main.rs

@@ -1,8 +1,12 @@
+// The signer only deploys on unix (permission-checked unix socket); other
+// hosts get a stub main so workspace-wide checks still build the target.
+#![cfg_attr(not(unix), allow(dead_code))]
+
 use std::{env, path::PathBuf, process::ExitCode};
 
-use op_collab_relay_locator_hsm::{
-    secure_file, server, KeyStore, SignerConfig, SignerError, SignerResult,
-};
+#[cfg(unix)]
+use op_collab_relay_locator_hsm::{secure_file, server, KeyStore, SignerConfig};
+use op_collab_relay_locator_hsm::{SignerError, SignerResult};
 use tracing_subscriber::EnvFilter;
 
 enum Command {
@@ -18,6 +22,7 @@ struct Arguments {
     config: PathBuf,
 }
 
+#[cfg(unix)]
 fn main() -> ExitCode {
     init_tracing();
     match run() {
@@ -29,6 +34,14 @@ fn main() -> ExitCode {
     }
 }
 
+#[cfg(not(unix))]
+fn main() -> ExitCode {
+    init_tracing();
+    eprintln!("locator HSM signer requires a unix host");
+    ExitCode::FAILURE
+}
+
+#[cfg(unix)]
 fn run() -> SignerResult<()> {
     let arguments = parse_arguments()?;
     let config_bytes = secure_file::read_config(&arguments.config)?;

crates/op-collab-transport/src/runtime_tests.rs

@@ -79,9 +79,13 @@ mod heartbeat_idle {
         TransportConfig {
             timeouts: TimeoutConfig {
                 heartbeat: Duration::from_millis(50),
-                idle: Duration::from_millis(400),
-                read_write: Duration::from_millis(400),
-                admission: Duration::from_millis(400),
+                // The transfer-idle deadline is what this module tests; 2s
+                // keeps the run short while leaving the handshake windows
+                // (capped at idle by config validation) wide enough that a
+                // loaded CI runner cannot flake the connect/admission phase.
+                idle: Duration::from_secs(2),
+                read_write: Duration::from_secs(2),
+                admission: Duration::from_secs(2),
                 ..TimeoutConfig::default()
             },
             ..TransportConfig::default()