Code review improvements: enhance maintainability and error handling

.gitignore

@@ -1,4 +1,5 @@
 # Compiled Binaries, Executables, and Libraries
+meshexec
 *.exe
 *.exe~
 *.dll

internal/targeting/evaluator.go

@@ -431,16 +431,29 @@ func (e *Evaluator) evaluateAST(ast *internal.TargetAST, device *internal.Device
 	}
 }
 
-// evaluateCondition evaluates a single condition against device information
+// evaluateCondition evaluates a single condition against device information.
+// Supports device attributes: name, role, os, arch, and custom tags.
+// Comparisons are case-insensitive for better usability.
+// Returns false (not error) when tags don't exist to support negative matching.
 func (e *Evaluator) evaluateCondition(condition string, device *internal.DeviceInfo) (bool, error) {
 	parts := strings.SplitN(condition, "=", 2)
 	if len(parts) != 2 {
-		return false, fmt.Errorf("invalid condition format: %s", condition)
+		return false, fmt.Errorf("invalid condition format: %s (expected 'attribute=value')", condition)
 	}
 
 	attribute := strings.TrimSpace(parts[0])
 	value := strings.TrimSpace(parts[1])
 
+	// Validate attribute name
+	if attribute == "" {
+		return false, fmt.Errorf("attribute cannot be empty")
+	}
+
+	// Validate value
+	if value == "" {
+		return false, fmt.Errorf("invalid condition format: %s (value cannot be empty)", condition)
+	}
+
 	// Remove quotes from value if present
 	if len(value) >= 2 && (value[0] == '"' && value[len(value)-1] == '"') {
 		value = value[1 : len(value)-1]

internal/tui/model.go

@@ -25,6 +25,21 @@ const (
 	tabCommands
 )
 
+// Output preview settings
+const (
+	maxOutputPreviewLength = 30
+	outputTruncateSuffix   = "..."
+	outputTruncateLength   = maxOutputPreviewLength - len(outputTruncateSuffix)
+)
+
+// Table formatting settings for results view
+const (
+	deviceColumnWidth   = 9
+	statusColumnWidth   = 6
+	exitCodeColumnWidth = 4
+	durationColumnWidth = 8
+)
+
 // simple peer list placeholder compatible with tests
 type peerListModel struct {
 	items []interface{}
@@ -492,12 +507,16 @@ func (m *model) renderResults() string {
 		if output == "" {
 			output = result.Stderr
 		}
-		if len(output) > 30 {
-			output = output[:27] + "..."
+		if len(output) > maxOutputPreviewLength {
+			output = output[:outputTruncateLength] + outputTruncateSuffix
 		}
 
-		row := fmt.Sprintf("│ %-9s │ %-6s │ %-4d │ %-8d │ %s",
-			result.Device, status, result.ExitCode, result.Duration, output)
+		row := fmt.Sprintf("│ %-*s │ %-*s │ %-*d │ %-*d │ %s",
+			deviceColumnWidth, result.Device,
+			statusColumnWidth, status,
+			exitCodeColumnWidth, result.ExitCode,
+			durationColumnWidth, result.Duration,
+			output)
 		rows = append(rows, row)
 	}