fix(process): let Program.Find validate existing paths

program.go

@@ -44,12 +44,16 @@ type Program struct {
 //
 //	if err := p.Find(); err != nil { return err }
 func (p *Program) Find() error {
-	if p.Name == "" {
+	target := p.Name
+	if target == "" {
+		target = p.Path
+	}
+	if target == "" {
 		return coreerr.E("Program.Find", "program name is empty", nil)
 	}
-	path, err := exec.LookPath(p.Name)
+	path, err := exec.LookPath(target)
 	if err != nil {
-		return coreerr.E("Program.Find", core.Sprintf("%q: not found in PATH", p.Name), ErrProgramNotFound)
+		return coreerr.E("Program.Find", core.Sprintf("%q: not found in PATH", target), ErrProgramNotFound)
 	}
 	p.Path = path
 	return nil

program_test.go

@@ -2,6 +2,7 @@ package process_test
 
 import (
 	"context"
+	"os/exec"
 	"path/filepath"
 	"testing"
 	"time"
@@ -32,6 +33,15 @@ func TestProgram_Find_UnknownBinary(t *testing.T) {
 	assert.ErrorIs(t, err, process.ErrProgramNotFound)
 }
 
+func TestProgram_Find_UsesExistingPath(t *testing.T) {
+	path, err := exec.LookPath("echo")
+	require.NoError(t, err)
+
+	p := &process.Program{Path: path}
+	require.NoError(t, p.Find())
+	assert.Equal(t, path, p.Path)
+}
+
 func TestProgram_Find_EmptyName(t *testing.T) {
 	p := &process.Program{}
 	require.Error(t, p.Find())