fix(agent): propagate discovered PATH to agent subprocesses

Prioritize the agent executable directory while preserving discovered
search paths for Pi package operations and CLI version probes.

Add coverage for PATH ordering and downstream command resolution.

src-tauri/src/tests/agent_configuration.rs

@@ -1919,6 +1919,67 @@ fn detected_agent_version_requires_a_real_version_value() {
     assert!(normalize_detected_agent_version(&"1".repeat(257)).is_none());
 }
 
+#[test]
+fn agent_command_path_prioritizes_the_executable_and_preserves_discovered_paths() {
+    let home = agent_test_home("command-path");
+    let executable_directory = home.join("node-runtime/bin");
+    let executable = executable_directory.join("pi");
+    fs::create_dir_all(&executable_directory).unwrap();
+
+    let path = agent_command_path(&home, &executable).unwrap();
+    let directories = env::split_paths(&path).collect::<Vec<_>>();
+
+    assert_eq!(directories.first(), Some(&executable_directory));
+    assert!(directories.contains(&home.join(".local/bin")));
+    if let Some(inherited_path) = env::var_os("PATH") {
+        for inherited_directory in env::split_paths(&inherited_path) {
+            assert!(directories.contains(&inherited_directory));
+        }
+    }
+
+    fs::remove_dir_all(home).unwrap();
+}
+
+#[test]
+fn agent_version_probe_exposes_the_executable_directory_to_child_commands() {
+    let home = agent_test_home("version-path");
+    let executable_directory = home.join("node-runtime/bin");
+    fs::create_dir_all(&executable_directory).unwrap();
+
+    #[cfg(target_os = "windows")]
+    let (executable, helper) = (
+        executable_directory.join("pi.cmd"),
+        executable_directory.join("agent-version-helper.cmd"),
+    );
+    #[cfg(not(target_os = "windows"))]
+    let (executable, helper) = (
+        executable_directory.join("pi"),
+        executable_directory.join("agent-version-helper"),
+    );
+
+    #[cfg(target_os = "windows")]
+    {
+        fs::write(&executable, "@echo off\r\nagent-version-helper.cmd\r\n").unwrap();
+        fs::write(&helper, "@echo off\r\necho pi 1.2.3\r\n").unwrap();
+    }
+    #[cfg(not(target_os = "windows"))]
+    {
+        use std::os::unix::fs::PermissionsExt;
+
+        fs::write(&executable, "#!/usr/bin/env sh\nagent-version-helper\n").unwrap();
+        fs::write(&helper, "#!/usr/bin/env sh\nprintf 'pi 1.2.3\\n'\n").unwrap();
+        fs::set_permissions(&executable, fs::Permissions::from_mode(0o755)).unwrap();
+        fs::set_permissions(&helper, fs::Permissions::from_mode(0o755)).unwrap();
+    }
+
+    assert_eq!(
+        read_agent_version(&executable, &home).as_deref(),
+        Some("pi 1.2.3")
+    );
+
+    fs::remove_dir_all(home).unwrap();
+}
+
 #[test]
 fn agent_probe_command_captures_output_before_timeout() {
     #[cfg(target_os = "windows")]