test: Add test coverage for 16 files (40.3% → 45.5%) (#463)

* test: Add test coverage for 16 files (40.3% -> 45.5%)

Add comprehensive tests for previously untested packages:
- internal/agent/state_test.go
- internal/cmd/errors_test.go
- internal/crew/types_test.go
- internal/doctor/errors_test.go
- internal/dog/types_test.go
- internal/mail/bd_test.go
- internal/opencode/plugin_test.go
- internal/rig/overlay_test.go
- internal/runtime/runtime_test.go
- internal/session/town_test.go
- internal/style/style_test.go
- internal/ui/markdown_test.go
- internal/ui/terminal_test.go
- internal/wisp/io_test.go
- internal/wisp/types_test.go
- internal/witness/types_test.go

style_test.go uses func(...string) to match lipgloss variadic Render signature.

* fix(lint): remove unused error return from buildCVSummary

buildCVSummary always returned nil for its error value, causing
golangci-lint to fail with "result 1 (error) is always nil".

The function handles errors internally by returning partial data,
so the error return was misleading. Removed it and updated caller.

internal/opencode/plugin_test.go

@@ -0,0 +1,153 @@
+package opencode
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestEnsurePluginAt_EmptyParameters(t *testing.T) {
+	// Test that empty pluginDir or pluginFile returns nil
+	t.Run("empty pluginDir", func(t *testing.T) {
+		err := EnsurePluginAt("/tmp/work", "", "plugin.js")
+		if err != nil {
+			t.Errorf("EnsurePluginAt() with empty pluginDir should return nil, got %v", err)
+		}
+	})
+
+	t.Run("empty pluginFile", func(t *testing.T) {
+		err := EnsurePluginAt("/tmp/work", "plugins", "")
+		if err != nil {
+			t.Errorf("EnsurePluginAt() with empty pluginFile should return nil, got %v", err)
+		}
+	})
+
+	t.Run("both empty", func(t *testing.T) {
+		err := EnsurePluginAt("/tmp/work", "", "")
+		if err != nil {
+			t.Errorf("EnsurePluginAt() with both empty should return nil, got %v", err)
+		}
+	})
+}
+
+func TestEnsurePluginAt_FileExists(t *testing.T) {
+	// Create a temporary directory
+	tmpDir := t.TempDir()
+
+	// Create the plugin file first
+	pluginDir := "plugins"
+	pluginFile := "gastown.js"
+	pluginPath := filepath.Join(tmpDir, pluginDir, pluginFile)
+
+	if err := os.MkdirAll(filepath.Dir(pluginPath), 0755); err != nil {
+		t.Fatalf("Failed to create test directory: %v", err)
+	}
+
+	// Write a placeholder file
+	existingContent := []byte("// existing plugin")
+	if err := os.WriteFile(pluginPath, existingContent, 0644); err != nil {
+		t.Fatalf("Failed to create test file: %v", err)
+	}
+
+	// EnsurePluginAt should not overwrite existing file
+	err := EnsurePluginAt(tmpDir, pluginDir, pluginFile)
+	if err != nil {
+		t.Fatalf("EnsurePluginAt() error = %v", err)
+	}
+
+	// Verify file content is unchanged
+	content, err := os.ReadFile(pluginPath)
+	if err != nil {
+		t.Fatalf("Failed to read plugin file: %v", err)
+	}
+	if string(content) != string(existingContent) {
+		t.Error("EnsurePluginAt() should not overwrite existing file")
+	}
+}
+
+func TestEnsurePluginAt_CreatesFile(t *testing.T) {
+	// Create a temporary directory
+	tmpDir := t.TempDir()
+
+	pluginDir := "plugins"
+	pluginFile := "gastown.js"
+	pluginPath := filepath.Join(tmpDir, pluginDir, pluginFile)
+
+	// Ensure plugin doesn't exist
+	if _, err := os.Stat(pluginPath); err == nil {
+		t.Fatal("Plugin file should not exist yet")
+	}
+
+	// Create the plugin
+	err := EnsurePluginAt(tmpDir, pluginDir, pluginFile)
+	if err != nil {
+		t.Fatalf("EnsurePluginAt() error = %v", err)
+	}
+
+	// Verify file was created
+	info, err := os.Stat(pluginPath)
+	if err != nil {
+		t.Fatalf("Plugin file was not created: %v", err)
+	}
+	if info.IsDir() {
+		t.Error("Plugin path should be a file, not a directory")
+	}
+
+	// Verify file has content
+	content, err := os.ReadFile(pluginPath)
+	if err != nil {
+		t.Fatalf("Failed to read plugin file: %v", err)
+	}
+	if len(content) == 0 {
+		t.Error("Plugin file should have content")
+	}
+}
+
+func TestEnsurePluginAt_CreatesDirectory(t *testing.T) {
+	// Create a temporary directory
+	tmpDir := t.TempDir()
+
+	pluginDir := "nested/plugins/dir"
+	pluginFile := "gastown.js"
+	pluginPath := filepath.Join(tmpDir, pluginDir, pluginFile)
+
+	// Create the plugin
+	err := EnsurePluginAt(tmpDir, pluginDir, pluginFile)
+	if err != nil {
+		t.Fatalf("EnsurePluginAt() error = %v", err)
+	}
+
+	// Verify directory was created
+	dirInfo, err := os.Stat(filepath.Dir(pluginPath))
+	if err != nil {
+		t.Fatalf("Plugin directory was not created: %v", err)
+	}
+	if !dirInfo.IsDir() {
+		t.Error("Plugin parent path should be a directory")
+	}
+}
+
+func TestEnsurePluginAt_FilePermissions(t *testing.T) {
+	// Create a temporary directory
+	tmpDir := t.TempDir()
+
+	pluginDir := "plugins"
+	pluginFile := "gastown.js"
+	pluginPath := filepath.Join(tmpDir, pluginDir, pluginFile)
+
+	err := EnsurePluginAt(tmpDir, pluginDir, pluginFile)
+	if err != nil {
+		t.Fatalf("EnsurePluginAt() error = %v", err)
+	}
+
+	info, err := os.Stat(pluginPath)
+	if err != nil {
+		t.Fatalf("Failed to stat plugin file: %v", err)
+	}
+
+	// Check file mode is 0644 (rw-r--r--)
+	expectedMode := os.FileMode(0644)
+	if info.Mode() != expectedMode {
+		t.Errorf("Plugin file mode = %v, want %v", info.Mode(), expectedMode)
+	}
+}