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/config/models.go

@@ -12,8 +12,6 @@ type skillChain struct {
 }
 
 type modelsFile struct {
-	Verifier     string                `yaml:"verifier"`
-	LlamaSwapURL string                `yaml:"llama_swap_url"`
 	DefaultChain []string              `yaml:"default_chain"`
 	Skills       map[string]skillChain `yaml:"skills"`
 }
@@ -34,23 +32,18 @@ func LoadModels(path string) (Models, error) {
 	return Models{data: f}, nil
 }
 
-// Verifier returns the model name to use for all local-tier output verification.
-func (m Models) Verifier() string { return m.data.Verifier }
-
-// LlamaSwapURL returns the llama-swap base URL for warm-state probing.
-func (m Models) LlamaSwapURL() string { return m.data.LlamaSwapURL }
-
-// ChainFor returns the ordered list of model names for a skill.
-// If override is non-empty, returns a single-entry chain (no escalation).
-// Falls back to default_chain when the skill has no explicit entry.
-func (m Models) ChainFor(skill, override string) []string {
+// ModelFor returns the primary model to use for a skill.
+// If override is non-empty, it is returned directly.
+// Falls back to default_chain[0] when the skill has no explicit entry.
+func (m Models) ModelFor(skill, override string) string {
 	if override != "" {
-		return []string{override}
+		return override
 	}
 	if sc, ok := m.data.Skills[skill]; ok && len(sc.Chain) > 0 {
-		return sc.Chain
+		return sc.Chain[0]
 	}
-	out := make([]string, len(m.data.DefaultChain))
-	copy(out, m.data.DefaultChain)
-	return out
+	if len(m.data.DefaultChain) > 0 {
+		return m.data.DefaultChain[0]
+	}
+	return ""
 }