test: extraer resolveWorkDir y tests unitarios de aislamiento

Extraer la logica de resolucion de working_dir a una funcion
resolveWorkDir() separada para hacerla testeable. Tres tests cubren:
- WorkingDir vacio → crea tmpdir con prefijo claude-agent-*
- WorkingDir configurado → crea el directorio y lo usa
- WorkingDir ya existente → lo usa sin error

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shell/llm/claudecode.go

@@ -59,24 +59,7 @@ func NewClaudeCodeComplete(cfg config.ClaudeCodeCfg, log *slog.Logger) coretypes
 	}
 
 	// Resolve working directory once at init time.
-	workDir := cfg.WorkingDir
-	if workDir == "" {
-		tmp, err := os.MkdirTemp("", "claude-agent-*")
-		if err != nil {
-			log.Error("claude-code: failed to create temp working dir", "err", err)
-			// Fall through — cmd.Dir will remain empty (inherits CWD).
-		} else {
-			workDir = tmp
-			log.Warn("claude-code working_dir is empty, using temporary directory",
-				"dir", workDir,
-			)
-		}
-	} else {
-		// Ensure configured directory exists.
-		if err := os.MkdirAll(workDir, 0o755); err != nil {
-			log.Error("claude-code: failed to create working dir", "dir", workDir, "err", err)
-		}
-	}
+	workDir := resolveWorkDir(cfg.WorkingDir, log)
 
 	return func(ctx context.Context, req coretypes.CompletionRequest) (coretypes.CompletionResponse, error) {
 		ctx, cancel := context.WithTimeout(ctx, timeout)
@@ -141,6 +124,29 @@ func NewClaudeCodeComplete(cfg config.ClaudeCodeCfg, log *slog.Logger) coretypes
 	}
 }
 
+// resolveWorkDir determines the working directory for the claude subprocess.
+// If configured is empty, it creates a temporary directory to avoid inheriting the launcher's CWD.
+// If configured is non-empty, it ensures the directory exists.
+func resolveWorkDir(configured string, log *slog.Logger) string {
+	if configured == "" {
+		tmp, err := os.MkdirTemp("", "claude-agent-*")
+		if err != nil {
+			log.Error("claude-code: failed to create temp working dir", "err", err)
+			return "" // Fall through — cmd.Dir will remain empty (inherits CWD).
+		}
+		log.Warn("claude-code working_dir is empty, using temporary directory",
+			"dir", tmp,
+		)
+		return tmp
+	}
+
+	// Ensure configured directory exists.
+	if err := os.MkdirAll(configured, 0o755); err != nil {
+		log.Error("claude-code: failed to create working dir", "dir", configured, "err", err)
+	}
+	return configured
+}
+
 // buildClaudeArgs constructs the CLI arguments for claude -p.
 func buildClaudeArgs(cfg config.ClaudeCodeCfg, req coretypes.CompletionRequest) []string {
 	args := []string{"--print", "--output-format", "json"}