docs: examples for every hard requirement + mort migration blueprint

Phase 7: nine runnable examples/ programs (parse, failover chains with
trailing alias, tiers, LLM_* env providers, multimodal, tool loop,
Generate[T], agent, skills); docs/mort-migration.md mapping mort's
go-llm/go-agentkit usage onto majordomo APIs with the planned additive
library extensions and conversion order; README finalized with the
complete matrix.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

examples/agent/main.go

@@ -0,0 +1,66 @@
+// Command agent demonstrates the agent loop: model + system prompt +
+// toolbox, run to completion with step observation.
+package main
+
+import (
+	"context"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"log"
+	"os"
+
+	"gitea.stevedudenhoeffer.com/steve/majordomo"
+	"gitea.stevedudenhoeffer.com/steve/majordomo/agent"
+)
+
+func main() {
+	model := flag.String("model", "ollama-cloud/minimax-m3:cloud", "model spec")
+	flag.Parse()
+
+	files := majordomo.NewToolbox("files",
+		majordomo.Tool{
+			Name:        "list_dir",
+			Description: "List the files in a directory.",
+			Parameters:  json.RawMessage(`{"type":"object","properties":{"path":{"type":"string"}},"required":["path"]}`),
+			Handler: func(_ context.Context, args json.RawMessage) (any, error) {
+				var p struct {
+					Path string `json:"path"`
+				}
+				if err := json.Unmarshal(args, &p); err != nil {
+					return nil, err
+				}
+				entries, err := os.ReadDir(p.Path)
+				if err != nil {
+					return nil, err
+				}
+				names := make([]string, 0, len(entries))
+				for _, e := range entries {
+					names = append(names, e.Name())
+				}
+				return names, nil
+			},
+		},
+	)
+
+	m, err := majordomo.Parse(*model)
+	if err != nil {
+		log.Fatalf("parse: %v", err)
+	}
+
+	a := agent.New(m, "You are a filesystem assistant. Use your tools; never invent file names.",
+		agent.WithToolbox(files),
+		agent.WithMaxSteps(6),
+		agent.WithStepObserver(func(s agent.Step) {
+			for _, call := range s.Response.ToolCalls {
+				fmt.Printf("  step %d: %s(%s)\n", s.Index, call.Name, call.Arguments)
+			}
+		}),
+	)
+
+	res, err := a.Run(context.Background(), "What Go files are in the current directory?")
+	if err != nil {
+		log.Fatalf("run: %v", err)
+	}
+	fmt.Printf("\n%s\n(%d steps, %d tokens)\n", res.Output, len(res.Steps), res.Usage.Total())
+}