feat(namepool): auto-select theme per rig based on name hash

Each rig now gets a deterministic theme based on its name instead of
always defaulting to mad-max. Uses a prime multiplier hash (×31) for
good distribution across themes. Same rig name always gets the same
theme. Users can still override with `gt namepool set`.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/polecat/manager_test.go

@@ -529,8 +529,9 @@ func TestReconcilePoolWith(t *testing.T) {
 			defer func() { _ = os.RemoveAll(tmpDir) }()
 
 			// Create rig and manager (nil tmux for unit test)
+			// Use "myrig" which hashes to mad-max theme
 			r := &rig.Rig{
-				Name: "testrig",
+				Name: "myrig",
 				Path: tmpDir,
 			}
 			m := NewManager(r, nil, nil)
@@ -591,8 +592,9 @@ func TestReconcilePoolWith_Allocation(t *testing.T) {
 	}
 	defer func() { _ = os.RemoveAll(tmpDir) }()
 
+	// Use "myrig" which hashes to mad-max theme
 	r := &rig.Rig{
-		Name: "testrig",
+		Name: "myrig",
 		Path: tmpDir,
 	}
 	m := NewManager(r, nil, nil)
@@ -627,8 +629,9 @@ func TestReconcilePoolWith_OrphanDoesNotBlockAllocation(t *testing.T) {
 	}
 	defer func() { _ = os.RemoveAll(tmpDir) }()
 
+	// Use "myrig" which hashes to mad-max theme
 	r := &rig.Rig{
-		Name: "testrig",
+		Name: "myrig",
 		Path: tmpDir,
 	}
 	m := NewManager(r, nil, nil)

internal/polecat/namepool.go

@@ -103,7 +103,7 @@ type NamePool struct {
 func NewNamePool(rigPath, rigName string) *NamePool {
 	return &NamePool{
 		RigName:      rigName,
-		Theme:        DefaultTheme,
+		Theme:        ThemeForRig(rigName),
 		InUse:        make(map[string]bool),
 		OverflowNext: DefaultPoolSize + 1,
 		MaxSize:      DefaultPoolSize,
@@ -352,6 +352,21 @@ func ListThemes() []string {
 	return themes
 }
 
+// ThemeForRig returns a deterministic theme for a rig based on its name.
+// This provides variety across rigs without requiring manual configuration.
+func ThemeForRig(rigName string) string {
+	themes := ListThemes()
+	if len(themes) == 0 {
+		return DefaultTheme
+	}
+	// Hash using prime multiplier for better distribution
+	var hash uint32
+	for _, b := range []byte(rigName) {
+		hash = hash*31 + uint32(b)
+	}
+	return themes[hash%uint32(len(themes))]
+}
+
 // GetThemeNames returns the names in a specific theme.
 func GetThemeNames(theme string) ([]string, error) {
 	if names, ok := BuiltinThemes[theme]; ok {

internal/polecat/namepool_test.go

@@ -13,7 +13,7 @@ func TestNamePool_Allocate(t *testing.T) {
 	}
 	defer func() { _ = os.RemoveAll(tmpDir) }()
 
-	pool := NewNamePool(tmpDir, "testrig")
+	pool := NewNamePoolWithConfig(tmpDir, "testrig", "mad-max", nil, DefaultPoolSize)
 
 	// First allocation should be first themed name (furiosa)
 	name, err := pool.Allocate()
@@ -41,7 +41,7 @@ func TestNamePool_Release(t *testing.T) {
 	}
 	defer func() { _ = os.RemoveAll(tmpDir) }()
 
-	pool := NewNamePool(tmpDir, "testrig")
+	pool := NewNamePoolWithConfig(tmpDir, "testrig", "mad-max", nil, DefaultPoolSize)
 
 	// Allocate first two
 	name1, _ := pool.Allocate()
@@ -68,7 +68,7 @@ func TestNamePool_PrefersOrder(t *testing.T) {
 	}
 	defer func() { _ = os.RemoveAll(tmpDir) }()
 
-	pool := NewNamePool(tmpDir, "testrig")
+	pool := NewNamePoolWithConfig(tmpDir, "testrig", "mad-max", nil, DefaultPoolSize)
 
 	// Allocate first 5
 	for i := 0; i < 5; i++ {
@@ -209,7 +209,7 @@ func TestNamePool_Reconcile(t *testing.T) {
 	}
 	defer func() { _ = os.RemoveAll(tmpDir) }()
 
-	pool := NewNamePool(tmpDir, "testrig")
+	pool := NewNamePoolWithConfig(tmpDir, "testrig", "mad-max", nil, DefaultPoolSize)
 
 	// Simulate existing polecats from filesystem
 	existing := []string{"slit", "valkyrie", "some-other-name"}
@@ -234,7 +234,7 @@ func TestNamePool_IsPoolName(t *testing.T) {
 	}
 	defer func() { _ = os.RemoveAll(tmpDir) }()
 
-	pool := NewNamePool(tmpDir, "testrig")
+	pool := NewNamePoolWithConfig(tmpDir, "testrig", "mad-max", nil, DefaultPoolSize)
 
 	tests := []struct {
 		name     string
@@ -263,7 +263,7 @@ func TestNamePool_ActiveNames(t *testing.T) {
 	}
 	defer func() { _ = os.RemoveAll(tmpDir) }()
 
-	pool := NewNamePool(tmpDir, "testrig")
+	pool := NewNamePoolWithConfig(tmpDir, "testrig", "mad-max", nil, DefaultPoolSize)
 
 	pool.Allocate() // furiosa
 	pool.Allocate() // nux
@@ -287,7 +287,7 @@ func TestNamePool_MarkInUse(t *testing.T) {
 	}
 	defer func() { _ = os.RemoveAll(tmpDir) }()
 
-	pool := NewNamePool(tmpDir, "testrig")
+	pool := NewNamePoolWithConfig(tmpDir, "testrig", "mad-max", nil, DefaultPoolSize)
 
 	// Mark some slots as in use
 	pool.MarkInUse("dementus")
@@ -417,7 +417,7 @@ func TestNamePool_Reset(t *testing.T) {
 	}
 	defer func() { _ = os.RemoveAll(tmpDir) }()
 
-	pool := NewNamePool(tmpDir, "testrig")
+	pool := NewNamePoolWithConfig(tmpDir, "testrig", "mad-max", nil, DefaultPoolSize)
 
 	// Allocate several names
 	for i := 0; i < 10; i++ {
@@ -441,3 +441,24 @@ func TestNamePool_Reset(t *testing.T) {
 		t.Errorf("expected furiosa after reset, got %s", name)
 	}
 }
+
+func TestThemeForRig(t *testing.T) {
+	// Different rigs should get different themes (with high probability)
+	themes := make(map[string]bool)
+	for _, rigName := range []string{"gastown", "beads", "myproject", "webapp"} {
+		themes[ThemeForRig(rigName)] = true
+	}
+	// Should have at least 2 different themes across 4 rigs
+	if len(themes) < 2 {
+		t.Errorf("expected variety in themes, got only %d unique theme(s)", len(themes))
+	}
+}
+
+func TestThemeForRigDeterministic(t *testing.T) {
+	// Same rig name should always get same theme
+	theme1 := ThemeForRig("myrig")
+	theme2 := ThemeForRig("myrig")
+	if theme1 != theme2 {
+		t.Errorf("theme not deterministic: got %q and %q", theme1, theme2)
+	}
+}