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/tdd/skill.go

@@ -4,17 +4,15 @@ import (
 	"context"
 	"encoding/json"
 
-	iexec "github.com/mathiasbq/supervisor/internal/exec"
 	"github.com/mathiasbq/supervisor/internal/registry"
 )
 
-// ExecutorFn allows injecting a test double for the executor.
-type ExecutorFn func(ctx context.Context, req iexec.Request) (iexec.Result, error)
+// CompleteFunc is the function used to call a local model.
+type CompleteFunc func(ctx context.Context, model, system, user string) (string, int64, error)
 
 type Config struct {
-	SystemPrompt  string
 	SkillPrompt   string
-	ExecutorFn    ExecutorFn // nil = no executor (tests that don't reach execute())
+	CompleteFunc  CompleteFunc // nil = no executor (tests that don't reach execute())
 	DefaultModel  string
 	SessionsDir   string // optional: path to brain/sessions/ for history injection
 	IngestBaseURL string // optional: base URL of ingestion server for brain context
@@ -44,7 +42,7 @@ func (s *Skill) Tools() []registry.ToolDef {
 	return []registry.ToolDef{
 		{
 			Name:        "tdd_red",
-			Description: "Write a failing test for the described behavior. Verifies the test fails before returning.",
+			Description: "Consult a local model for help writing a failing test for the described behavior.",
 			InputSchema: schema(
 				[]string{"project_root", "spec"},
 				map[string]any{
@@ -57,7 +55,7 @@ func (s *Skill) Tools() []registry.ToolDef {
 		},
 		{
 			Name:        "tdd_green",
-			Description: "Write minimal implementation to make the test at test_path pass.",
+			Description: "Consult a local model for implementation ideas to make the test at test_path pass.",
 			InputSchema: schema(
 				[]string{"project_root", "test_path"},
 				map[string]any{
@@ -71,7 +69,7 @@ func (s *Skill) Tools() []registry.ToolDef {
 		},
 		{
 			Name:        "tdd_refactor",
-			Description: "Refactor the implementation at impl_path while keeping tests green.",
+			Description: "Consult a local model for refactoring suggestions for impl_path while keeping tests green.",
 			InputSchema: schema(
 				[]string{"project_root", "test_path", "impl_path"},
 				map[string]any{