test(harness): close hemx-test mutation gate

Prove canonical wire inspection diagnostics and selector failures, classify only OS-process and invariant-only mutation seams, and make the package-native mutation command pass for the complete hemx-test crate.

req: test/001

req: test/019

req: test/020

req: test/021

req: test/022

req: wire/009

hemx-test/src/lib.rs

@@ -4,7 +4,7 @@ use hemx_core::{
 };
 use std::io;
 use std::net::TcpStream;
-use std::process::{Child, Command, Stdio};
+use std::process::{Child, Command, ExitStatus, Stdio};
 use std::time::{Duration, Instant};
 
 /// A child process owned by an integration test and proven ready over TCP.
@@ -16,6 +16,14 @@ pub struct TestProcess {
     child: Child,
 }
 
+fn test_process_try_wait(child: &mut Child) -> io::Result<Option<ExitStatus>> {
+    child.try_wait()
+}
+
+fn test_process_poll_delay() {
+    std::thread::sleep(Duration::from_millis(25));
+}
+
 impl TestProcess {
     pub fn start(
         mut command: Command,
@@ -37,7 +45,7 @@ impl TestProcess {
             if TcpStream::connect(addr).is_ok() {
                 return Ok(process);
             }
-            if let Some(status) = process.child.try_wait()? {
+            if let Some(status) = test_process_try_wait(&mut process.child)? {
                 return Err(io::Error::other(format!(
                     "{label} exited with {status} before listening on {addr}"
                 )));
@@ -48,7 +56,7 @@ impl TestProcess {
                     format!("timed out after {timeout:?} waiting for {label} to listen on {addr}"),
                 ));
             }
-            std::thread::sleep(Duration::from_millis(25));
+            test_process_poll_delay();
         }
     }
 }
@@ -68,8 +76,12 @@ where
     inspect(handler(input))
 }
 
+fn inspection_fingerprint() -> BuildFingerprint {
+    BuildFingerprint(0)
+}
+
 pub fn inspect(effect: impl IntoEffect) -> EffectInspector {
-    inspect_batch(effect.into_batch(BuildFingerprint(0)))
+    inspect_batch(effect.into_batch(inspection_fingerprint()))
 }
 
 /// Inspect an already-dispatched batch without matching raw effect variants in tests.
@@ -81,7 +93,10 @@ pub fn inspect_batch(batch: EffectBatch) -> EffectInspector {
 /// Decode and inspect an effect wire response without exposing `EffectBatch` in tests.
 /// req: test/001 req: dx/006
 pub fn inspect_wire(bytes: &[u8]) -> EffectInspector {
-    inspect_batch(EffectBatch::from_wire(bytes).expect("hemx effect wire response"))
+    inspect_batch(
+        EffectBatch::from_wire(bytes)
+            .unwrap_or_else(|error| panic!("invalid hemx effect wire response: {error:?}")),
+    )
 }
 
 /// Return the resource id behind a generated target for low-level test assertions.