fix(refinery): use rig's default_branch instead of hardcoded 'main'

- Add DefaultBranch field to RoleData struct
- Update refinery.md.tmpl to use {{ .DefaultBranch }} template variable
- Populate DefaultBranch from rig config in prime.go and rig/manager.go
- Default to 'main' if not configured
- Add test verifying DefaultBranch rendering in refinery template

Fixes issue where refinery agents merged to master instead of the
configured default branch (e.g., 'develop' or 'develop-cstar').

internal/templates/templates_test.go

@@ -26,6 +26,7 @@ func TestRenderRole_Mayor(t *testing.T) {
 		TownRoot:      "/test/town",
 		TownName:      "town",
 		WorkDir:       "/test/town",
+		DefaultBranch: "main",
 		MayorSession:  "gt-town-mayor",
 		DeaconSession: "gt-town-deacon",
 	}
@@ -59,6 +60,7 @@ func TestRenderRole_Polecat(t *testing.T) {
 		TownRoot:      "/test/town",
 		TownName:      "town",
 		WorkDir:       "/test/town/myrig/polecats/TestCat",
+		DefaultBranch: "main",
 		Polecat:       "TestCat",
 		MayorSession:  "gt-town-mayor",
 		DeaconSession: "gt-town-deacon",
@@ -92,6 +94,7 @@ func TestRenderRole_Deacon(t *testing.T) {
 		TownRoot:      "/test/town",
 		TownName:      "town",
 		WorkDir:       "/test/town",
+		DefaultBranch: "main",
 		MayorSession:  "gt-town-mayor",
 		DeaconSession: "gt-town-deacon",
 	}
@@ -119,6 +122,53 @@ func TestRenderRole_Deacon(t *testing.T) {
 	}
 }
 
+func TestRenderRole_Refinery_DefaultBranch(t *testing.T) {
+	tmpl, err := New()
+	if err != nil {
+		t.Fatalf("New() error = %v", err)
+	}
+
+	// Test with custom default branch (e.g., "develop")
+	data := RoleData{
+		Role:          "refinery",
+		RigName:       "myrig",
+		TownRoot:      "/test/town",
+		TownName:      "town",
+		WorkDir:       "/test/town/myrig/refinery/rig",
+		DefaultBranch: "develop",
+		MayorSession:  "gt-town-mayor",
+		DeaconSession: "gt-town-deacon",
+	}
+
+	output, err := tmpl.RenderRole("refinery", data)
+	if err != nil {
+		t.Fatalf("RenderRole() error = %v", err)
+	}
+
+	// Check that the custom default branch is used in git commands
+	if !strings.Contains(output, "origin/develop") {
+		t.Error("output missing 'origin/develop' - DefaultBranch not being used for rebase")
+	}
+	if !strings.Contains(output, "git checkout develop") {
+		t.Error("output missing 'git checkout develop' - DefaultBranch not being used for checkout")
+	}
+	if !strings.Contains(output, "git push origin develop") {
+		t.Error("output missing 'git push origin develop' - DefaultBranch not being used for push")
+	}
+
+	// Verify it does NOT contain hardcoded "main" in git commands
+	// (main may appear in other contexts like "main branch" descriptions, so we check specific patterns)
+	if strings.Contains(output, "git rebase origin/main") {
+		t.Error("output still contains hardcoded 'git rebase origin/main' - should use DefaultBranch")
+	}
+	if strings.Contains(output, "git checkout main") {
+		t.Error("output still contains hardcoded 'git checkout main' - should use DefaultBranch")
+	}
+	if strings.Contains(output, "git push origin main") {
+		t.Error("output still contains hardcoded 'git push origin main' - should use DefaultBranch")
+	}
+}
+
 func TestRenderMessage_Spawn(t *testing.T) {
 	tmpl, err := New()
 	if err != nil {