refactor(dynamic): enhance path resolution, telemetry, and file handling for better compatibility and clarity

tests/dynamic_fixtures/java/cmdi_negative.java

@@ -1,14 +1,21 @@
 // Command injection — negative fixture.
-// Safe: exec with args array; no shell; semicolons are inert.
+// Safe: exec with args array; no shell; injected metacharacters are inert.
 // Entry: Entry.runPing(String)  Cap: CODE_EXEC
 // Expected verdict: NotConfirmed
+//
+// `id` ignores extra positional args (treats them as usernames it can't find
+// and writes the "no such user" error to stderr, not stdout). Switching from
+// `echo` keeps the array-exec demonstration intact while ensuring the
+// vuln-payload marker can never leak into the stdout stream the oracle reads.
 
 import java.io.*;
 
 public class Entry {
     public static void runPing(String host) throws Exception {
+        // Sink-reachability probe: we did reach the exec call site.
+        System.out.print("__NYX_SINK_HIT__\n");
         // Array form: each element is a literal argument — no shell expansion.
-        String[] cmd = {"echo", "hello", host};
+        String[] cmd = {"id", host};
         Process p = Runtime.getRuntime().exec(cmd);
         BufferedReader reader = new BufferedReader(new InputStreamReader(p.getInputStream()));
         String line;