refactor: replace orchestrator/verifier chain with direct LiteLLM calls

Drop the three-layer Claude subprocess orchestration (local model →
Claude verifier → cloud escalation). Skills now call LiteLLM directly
and return plain text to Claude Code, which decides what to do with it.

- Delete executor, orchestrator, verifier, result, attempts packages
- Simplify LiteLLMExecutor: Run(Request)→Result becomes Complete(model,sys,user)→(string,int64,error)
- Replace ExecutorFn with CompleteFunc in all 6 skill configs
- Rewrite all skill handlers to call Complete and return {"text","model","duration_ms"}
- Simplify config/models: remove Verifier/LlamaSwapURL, add ModelFor
- Bump version to v0.5.0

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

internal/skills/retrospective/handlers_test.go

@@ -6,7 +6,6 @@ import (
 	"encoding/json"
 	"testing"
 
-	iexec "github.com/mathiasbq/supervisor/internal/exec"
 	"github.com/mathiasbq/supervisor/internal/skills/retrospective"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -20,20 +19,14 @@ func TestHandle_Retrospective_RequiresSessionID(t *testing.T) {
 }
 
 func TestHandle_Retrospective_BuildsPromptWithSessionLog(t *testing.T) {
-	var capturedReq iexec.Request
+	var capturedTask string
 	s := retrospective.New(retrospective.Config{
 		SkillPrompt:  "retrospective discipline",
 		DefaultModel: "ollama/test",
-		SessionsDir:  t.TempDir(), // empty dir, no session file — that's OK, session.Read returns nil
-		ExecutorFn: func(_ context.Context, req iexec.Request) (iexec.Result, error) {
-			capturedReq = req
-			return iexec.Result{
-				Status:   "pass",
-				Phase:    "retrospective",
-				Skill:    "retrospective",
-				Verified: true,
-				Message:  "wrote 2 entries to brain",
-			}, nil
+		SessionsDir:  t.TempDir(),
+		CompleteFunc: func(_ context.Context, _, _, user string) (string, int64, error) {
+			capturedTask = user
+			return "Key insight: the team resolved a tricky nil pointer issue via careful logging.", 75, nil
 		},
 	})
 
@@ -41,9 +34,8 @@ func TestHandle_Retrospective_BuildsPromptWithSessionLog(t *testing.T) {
 	out, err := s.Handle(context.Background(), "retrospective", args)
 	require.NoError(t, err)
 
-	var result iexec.Result
+	var result map[string]any
 	require.NoError(t, json.Unmarshal(out, &result))
-	assert.Equal(t, "pass", result.Status)
-	assert.Contains(t, capturedReq.SkillPrompt, "retrospective discipline")
-	assert.Contains(t, capturedReq.TaskPrompt, "empty-session")
+	assert.Contains(t, result["text"], "nil pointer")
+	assert.Contains(t, capturedTask, "empty-session")
 }