feat(types): remove Gas Town types from core built-in types

Core beads built-in types now only include work types:
- bug, feature, task, epic, chore

Gas Town types (molecule, gate, convoy, merge-request, slot, agent,
role, rig, event, message) are now "well-known custom types":
- Constants still exist for code convenience
- Require types.custom configuration for validation
- bd types command shows core types and configured custom types

Changes:
- types.go: Separate core work types from well-known custom types
- IsValid(): Only accepts core work types
- bd types: Updated to show core types and custom types from config
- memory.go: Use ValidateWithCustom for custom type support
- multirepo.go: Only check core types as built-in
- Updated all tests to configure custom types

This allows Gas Town (and other projects) to define their own types
via config while keeping beads core focused on work tracking.

Closes: bd-find4

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

internal/storage/memory/memory.go

@@ -190,8 +190,17 @@ func (m *MemoryStorage) CreateIssue(ctx context.Context, issue *types.Issue, act
 	m.mu.Lock()
 	defer m.mu.Unlock()
 
-	// Validate
-	if err := issue.Validate(); err != nil {
+	// Get custom types and statuses for validation
+	var customTypes, customStatuses []string
+	if typeStr := m.config["types.custom"]; typeStr != "" {
+		customTypes = parseCustomStatuses(typeStr)
+	}
+	if statusStr := m.config["status.custom"]; statusStr != "" {
+		customStatuses = parseCustomStatuses(statusStr)
+	}
+
+	// Validate with custom types
+	if err := issue.ValidateWithCustom(customStatuses, customTypes); err != nil {
 		return fmt.Errorf("validation failed: %w", err)
 	}
 
@@ -243,9 +252,18 @@ func (m *MemoryStorage) CreateIssues(ctx context.Context, issues []*types.Issue,
 	m.mu.Lock()
 	defer m.mu.Unlock()
 
+	// Get custom types and statuses for validation
+	var customTypes, customStatuses []string
+	if typeStr := m.config["types.custom"]; typeStr != "" {
+		customTypes = parseCustomStatuses(typeStr)
+	}
+	if statusStr := m.config["status.custom"]; statusStr != "" {
+		customStatuses = parseCustomStatuses(statusStr)
+	}
+
 	// Validate all first
 	for i, issue := range issues {
-		if err := issue.Validate(); err != nil {
+		if err := issue.ValidateWithCustom(customStatuses, customTypes); err != nil {
 			return fmt.Errorf("validation failed for issue %d: %w", i, err)
 		}
 	}

internal/storage/memory/memory_test.go

@@ -21,6 +21,12 @@ func setupTestMemory(t *testing.T) *MemoryStorage {
 		t.Fatalf("failed to set issue_prefix: %v", err)
 	}
 
+	// Configure Gas Town custom types for test compatibility (bd-find4)
+	// These types are no longer built-in but many tests use them
+	if err := store.SetConfig(ctx, "types.custom", "message,merge-request,molecule,gate,agent,role,rig,convoy,event,slot"); err != nil {
+		t.Fatalf("failed to set types.custom: %v", err)
+	}
+
 	return store
 }