refactor(routing): rename local/claude to fast/thinking model pair

The routing decision is about reasoning capacity, not cost or provider.
Fast model (koala/qwen35-9b-fast) handles high-pass-rate calls; thinking
model (iguana/gemma4-26b) handles low-pass-rate calls. Removes the
implicit Anthropic dependency from the routing pod — both models go
through LiteLLM.

Renames: HYPERGUILD_LOCAL_MODEL → HYPERGUILD_FAST_MODEL,
HYPERGUILD_CLAUDE_MODEL → HYPERGUILD_THINKING_MODEL,
Router.LocalModel → FastModel, Router.ClaudeModel → ThinkingModel,
log decision "claude_fallback" → "thinking_fallback".

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

internal/routing/router_test.go

@@ -49,12 +49,12 @@ func newRouter(t *testing.T, llm *fakeLLM, passRate float64) (*routing.Router, *
 	t.Cleanup(brain.Close)
 
 	r := &routing.Router{
-		Fetcher:     routing.NewFetcher(brain.URL, "7d", time.Minute),
-		Logger:      routing.NewLogger(brain.URL),
-		Policy:      routing.Policy{Floor: 0.9, Ceil: 0.7},
-		LocalModel:  "qwen35",
-		ClaudeModel: "claude-sonnet-4-6",
-		Complete:    llm.Complete,
+		Fetcher:       routing.NewFetcher(brain.URL, "7d", time.Minute),
+		Logger:        routing.NewLogger(brain.URL),
+		Policy:        routing.Policy{Floor: 0.9, Ceil: 0.7},
+		FastModel:     "koala/qwen35-9b-fast",
+		ThinkingModel: "iguana/gemma4-26b",
+		Complete:      llm.Complete,
 	}
 	return r, brain, brain
 }
@@ -72,10 +72,10 @@ func TestRouterRoutesLocalAtHighPassRate(t *testing.T) {
 	llm.mu.Lock()
 	defer llm.mu.Unlock()
 	require.Len(t, llm.calls, 1)
-	assert.Equal(t, "qwen35", llm.calls[0].Model)
+	assert.Equal(t, "koala/qwen35-9b-fast", llm.calls[0].Model)
 }
 
-func TestRouterRoutesClaudeAtLowPassRate(t *testing.T) {
+func TestRouterRoutesThinkingAtLowPassRate(t *testing.T) {
 	llm := &fakeLLM{resp: "ok"}
 	r, _, _ := newRouter(t, llm, 0.3)
 
@@ -87,12 +87,12 @@ func TestRouterRoutesClaudeAtLowPassRate(t *testing.T) {
 	llm.mu.Lock()
 	defer llm.mu.Unlock()
 	require.Len(t, llm.calls, 1)
-	assert.Equal(t, "claude-sonnet-4-6", llm.calls[0].Model)
+	assert.Equal(t, "iguana/gemma4-26b", llm.calls[0].Model)
 }
 
-func TestRouterFailsOpenLocalErrorToClaude(t *testing.T) {
-	llm := &fakeLLM{resp: "ok-after-fallback", err: errors.New("local boom"), errOn: "qwen35"}
-	r, _, _ := newRouter(t, llm, 0.95) // would route local
+func TestRouterFailsOpenFastErrorToThinking(t *testing.T) {
+	llm := &fakeLLM{resp: "ok-after-fallback", err: errors.New("fast boom"), errOn: "koala/qwen35-9b-fast"}
+	r, _, _ := newRouter(t, llm, 0.95) // would route fast
 
 	out, _, err := r.Run(context.Background(), routing.RunInput{
 		Skill: "review", System: "sys", User: "user", SessionID: "s3",
@@ -103,12 +103,12 @@ func TestRouterFailsOpenLocalErrorToClaude(t *testing.T) {
 	llm.mu.Lock()
 	defer llm.mu.Unlock()
 	require.Len(t, llm.calls, 2)
-	assert.Equal(t, "qwen35", llm.calls[0].Model)
-	assert.Equal(t, "claude-sonnet-4-6", llm.calls[1].Model)
+	assert.Equal(t, "koala/qwen35-9b-fast", llm.calls[0].Model)
+	assert.Equal(t, "iguana/gemma4-26b", llm.calls[1].Model)
 }
 
-func TestRouterDefaultsToLocalWhenBrainUnreachable(t *testing.T) {
-	// Brain returns 500 → fetcher errors → router treats pass rate as nil → local.
+func TestRouterDefaultsToFastWhenBrainUnreachable(t *testing.T) {
+	// Brain returns 500 → fetcher errors → router treats pass rate as nil → fast.
 	brain := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
 		http.Error(w, "down", http.StatusInternalServerError)
 	}))
@@ -116,12 +116,12 @@ func TestRouterDefaultsToLocalWhenBrainUnreachable(t *testing.T) {
 
 	llm := &fakeLLM{resp: "ok"}
 	r := &routing.Router{
-		Fetcher:     routing.NewFetcher(brain.URL, "7d", time.Minute),
-		Logger:      routing.NewLogger(brain.URL),
-		Policy:      routing.Policy{Floor: 0.9, Ceil: 0.7},
-		LocalModel:  "qwen35",
-		ClaudeModel: "claude-sonnet-4-6",
-		Complete:    llm.Complete,
+		Fetcher:       routing.NewFetcher(brain.URL, "7d", time.Minute),
+		Logger:        routing.NewLogger(brain.URL),
+		Policy:        routing.Policy{Floor: 0.9, Ceil: 0.7},
+		FastModel:     "koala/qwen35-9b-fast",
+		ThinkingModel: "iguana/gemma4-26b",
+		Complete:      llm.Complete,
 	}
 
 	_, _, err := r.Run(context.Background(), routing.RunInput{
@@ -132,5 +132,5 @@ func TestRouterDefaultsToLocalWhenBrainUnreachable(t *testing.T) {
 	llm.mu.Lock()
 	defer llm.mu.Unlock()
 	require.Len(t, llm.calls, 1)
-	assert.Equal(t, "qwen35", llm.calls[0].Model)
+	assert.Equal(t, "koala/qwen35-9b-fast", llm.calls[0].Model)
 }