feat(templates): recover local override support for role templates

Cherry-picked from lost commit 123d0b2b. Adds ability to override
embedded role templates at town or rig level:
- Town: <townRoot>/templates/roles/<role>.md.tmpl
- Rig: <rigPath>/templates/roles/<role>.md.tmpl

New APIs:
- NewWithOverrides(townRoot, rigPath string)
- HasRoleOverride(role string) bool
- RoleOverrideCount() int

Recovered by: gt-vjhf

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

internal/templates/templates_test.go

@@ -1,6 +1,7 @@
 package templates
 
 import (
+	"os"
 	"strings"
 	"testing"
 )
@@ -295,3 +296,164 @@ func TestGetAllRoleTemplates_ContentValidity(t *testing.T) {
 		}
 	}
 }
+
+func TestNewWithOverrides_NoOverrides(t *testing.T) {
+	// When no override paths exist, should work like New()
+	tmpl, err := NewWithOverrides("/nonexistent/town", "/nonexistent/rig")
+	if err != nil {
+		t.Fatalf("NewWithOverrides() error = %v", err)
+	}
+	if tmpl == nil {
+		t.Fatal("NewWithOverrides() returned nil")
+	}
+
+	// Should have no overrides
+	if tmpl.RoleOverrideCount() != 0 {
+		t.Errorf("RoleOverrideCount() = %d, want 0", tmpl.RoleOverrideCount())
+	}
+
+	// Should still render embedded templates
+	data := RoleData{
+		Role:    "polecat",
+		RigName: "myrig",
+		Polecat: "TestCat",
+	}
+	output, err := tmpl.RenderRole("polecat", data)
+	if err != nil {
+		t.Fatalf("RenderRole() error = %v", err)
+	}
+	if !strings.Contains(output, "Polecat Context") {
+		t.Error("embedded template not rendered correctly")
+	}
+}
+
+func TestNewWithOverrides_WithOverride(t *testing.T) {
+	// Create a temp directory with an override template
+	tempDir := t.TempDir()
+	overrideDir := tempDir + "/templates/roles"
+	if err := os.MkdirAll(overrideDir, 0755); err != nil {
+		t.Fatalf("failed to create override dir: %v", err)
+	}
+
+	// Write a simple override template
+	overrideContent := `# Custom Polecat Context
+You are polecat {{ .Polecat }} with custom instructions.
+Rig: {{ .RigName }}
+`
+	if err := os.WriteFile(overrideDir+"/polecat.md.tmpl", []byte(overrideContent), 0644); err != nil {
+		t.Fatalf("failed to write override template: %v", err)
+	}
+
+	// Create Templates with the override
+	tmpl, err := NewWithOverrides("", tempDir)
+	if err != nil {
+		t.Fatalf("NewWithOverrides() error = %v", err)
+	}
+
+	// Should have one override
+	if tmpl.RoleOverrideCount() != 1 {
+		t.Errorf("RoleOverrideCount() = %d, want 1", tmpl.RoleOverrideCount())
+	}
+
+	// Should report polecat as having override
+	if !tmpl.HasRoleOverride("polecat") {
+		t.Error("HasRoleOverride('polecat') = false, want true")
+	}
+	if tmpl.HasRoleOverride("mayor") {
+		t.Error("HasRoleOverride('mayor') = true, want false")
+	}
+
+	// Render should use override
+	data := RoleData{
+		Role:    "polecat",
+		RigName: "myrig",
+		Polecat: "TestCat",
+	}
+	output, err := tmpl.RenderRole("polecat", data)
+	if err != nil {
+		t.Fatalf("RenderRole() error = %v", err)
+	}
+
+	// Should contain custom content, not embedded
+	if !strings.Contains(output, "Custom Polecat Context") {
+		t.Error("override template not used - missing 'Custom Polecat Context'")
+	}
+	if strings.Contains(output, "Idle Polecat Heresy") {
+		t.Error("embedded template used instead of override")
+	}
+	if !strings.Contains(output, "TestCat") {
+		t.Error("template variable not expanded")
+	}
+}
+
+func TestNewWithOverrides_RigOverridesTown(t *testing.T) {
+	// Create temp dirs for both town and rig overrides
+	townDir := t.TempDir()
+	rigDir := t.TempDir()
+
+	townOverrideDir := townDir + "/templates/roles"
+	rigOverrideDir := rigDir + "/templates/roles"
+
+	if err := os.MkdirAll(townOverrideDir, 0755); err != nil {
+		t.Fatalf("failed to create town override dir: %v", err)
+	}
+	if err := os.MkdirAll(rigOverrideDir, 0755); err != nil {
+		t.Fatalf("failed to create rig override dir: %v", err)
+	}
+
+	// Write town override
+	townContent := "# Town Polecat\nTown override: {{ .Polecat }}"
+	if err := os.WriteFile(townOverrideDir+"/polecat.md.tmpl", []byte(townContent), 0644); err != nil {
+		t.Fatalf("failed to write town override: %v", err)
+	}
+
+	// Write rig override (should win)
+	rigContent := "# Rig Polecat\nRig override: {{ .Polecat }}"
+	if err := os.WriteFile(rigOverrideDir+"/polecat.md.tmpl", []byte(rigContent), 0644); err != nil {
+		t.Fatalf("failed to write rig override: %v", err)
+	}
+
+	// Create Templates with both overrides
+	tmpl, err := NewWithOverrides(townDir, rigDir)
+	if err != nil {
+		t.Fatalf("NewWithOverrides() error = %v", err)
+	}
+
+	// Render should use rig override (higher precedence)
+	data := RoleData{Polecat: "TestCat"}
+	output, err := tmpl.RenderRole("polecat", data)
+	if err != nil {
+		t.Fatalf("RenderRole() error = %v", err)
+	}
+
+	if !strings.Contains(output, "Rig Polecat") {
+		t.Error("rig override not used")
+	}
+	if strings.Contains(output, "Town Polecat") {
+		t.Error("town override used instead of rig override")
+	}
+}
+
+func TestNewWithOverrides_InvalidTemplate(t *testing.T) {
+	// Create a temp directory with an invalid template
+	tempDir := t.TempDir()
+	overrideDir := tempDir + "/templates/roles"
+	if err := os.MkdirAll(overrideDir, 0755); err != nil {
+		t.Fatalf("failed to create override dir: %v", err)
+	}
+
+	// Write an invalid template (unclosed action)
+	invalidContent := "# Invalid Template\n{{ .Polecat"
+	if err := os.WriteFile(overrideDir+"/polecat.md.tmpl", []byte(invalidContent), 0644); err != nil {
+		t.Fatalf("failed to write invalid template: %v", err)
+	}
+
+	// Should return error for invalid template
+	_, err := NewWithOverrides("", tempDir)
+	if err == nil {
+		t.Error("NewWithOverrides() should fail with invalid template")
+	}
+	if !strings.Contains(err.Error(), "parsing override template") {
+		t.Errorf("error should mention parsing override template: %v", err)
+	}
+}