Add go-llm v2: redesigned API for simpler LLM abstraction

v2 is a new Go module (v2/) with a dramatically simpler API:
- Unified Message type (no more Input marker interface)
- Define[T] for ergonomic tool creation with standard context.Context
- Chat session with automatic tool-call loop (agent loop)
- Streaming via pull-based StreamReader
- MCP one-call connect (MCPStdioServer, MCPHTTPServer, MCPSSEServer)
- Middleware support (logging, retry, timeout, usage tracking)
- Decoupled JSON Schema (map[string]any, no provider coupling)
- Sample tools: WebSearch, Browser, Exec, ReadFile, WriteFile, HTTP
- Providers: OpenAI, Anthropic, Google (all with streaming)

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

v2/tools/exec.go

@@ -0,0 +1,101 @@
+package tools
+
+import (
+	"context"
+	"fmt"
+	"os/exec"
+	"runtime"
+	"strings"
+	"time"
+
+	llm "gitea.stevedudenhoeffer.com/steve/go-llm/v2"
+)
+
+// ExecParams defines parameters for the exec tool.
+type ExecParams struct {
+	Command string `json:"command" description:"The shell command to execute"`
+}
+
+// ExecOption configures the exec tool.
+type ExecOption func(*execConfig)
+
+type execConfig struct {
+	allowedCommands []string
+	workDir         string
+	timeout         time.Duration
+}
+
+// WithAllowedCommands restricts which commands can be executed.
+// If empty, all commands are allowed.
+func WithAllowedCommands(cmds []string) ExecOption {
+	return func(c *execConfig) { c.allowedCommands = cmds }
+}
+
+// WithWorkDir sets the working directory for command execution.
+func WithWorkDir(dir string) ExecOption {
+	return func(c *execConfig) { c.workDir = dir }
+}
+
+// WithExecTimeout sets the maximum execution time.
+func WithExecTimeout(d time.Duration) ExecOption {
+	return func(c *execConfig) { c.timeout = d }
+}
+
+// Exec creates a shell command execution tool.
+//
+// Example:
+//
+//	tools := llm.NewToolBox(
+//	    tools.Exec(tools.WithAllowedCommands([]string{"ls", "cat", "grep"})),
+//	)
+func Exec(opts ...ExecOption) llm.Tool {
+	cfg := &execConfig{
+		timeout: 30 * time.Second,
+	}
+	for _, opt := range opts {
+		opt(cfg)
+	}
+
+	return llm.Define[ExecParams]("exec", "Execute a shell command and return its output",
+		func(ctx context.Context, p ExecParams) (string, error) {
+			// Check allowed commands
+			if len(cfg.allowedCommands) > 0 {
+				parts := strings.Fields(p.Command)
+				if len(parts) == 0 {
+					return "", fmt.Errorf("empty command")
+				}
+				allowed := false
+				for _, cmd := range cfg.allowedCommands {
+					if parts[0] == cmd {
+						allowed = true
+						break
+					}
+				}
+				if !allowed {
+					return "", fmt.Errorf("command %q is not in the allowed list", parts[0])
+				}
+			}
+
+			ctx, cancel := context.WithTimeout(ctx, cfg.timeout)
+			defer cancel()
+
+			var cmd *exec.Cmd
+			if runtime.GOOS == "windows" {
+				cmd = exec.CommandContext(ctx, "cmd", "/C", p.Command)
+			} else {
+				cmd = exec.CommandContext(ctx, "sh", "-c", p.Command)
+			}
+
+			if cfg.workDir != "" {
+				cmd.Dir = cfg.workDir
+			}
+
+			output, err := cmd.CombinedOutput()
+			if err != nil {
+				return fmt.Sprintf("Error: %s\nOutput: %s", err.Error(), string(output)), nil
+			}
+
+			return string(output), nil
+		},
+	)
+}