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/types/types.go

@@ -476,13 +476,20 @@ func (s Status) IsValidWithCustom(customStatuses []string) bool {
 // IssueType categorizes the kind of work
 type IssueType string
 
-// Issue type constants
+// Core work type constants - these are the built-in types that beads validates.
+// All other types require configuration via types.custom in config.yaml.
+const (
+	TypeBug     IssueType = "bug"
+	TypeFeature IssueType = "feature"
+	TypeTask    IssueType = "task"
+	TypeEpic    IssueType = "epic"
+	TypeChore   IssueType = "chore"
+)
+
+// Well-known custom types - constants for code convenience.
+// These are NOT built-in types and require types.custom configuration for validation.
+// Used by Gas Town and other infrastructure that extends beads.
 const (
-	TypeBug          IssueType = "bug"
-	TypeFeature      IssueType = "feature"
-	TypeTask         IssueType = "task"
-	TypeEpic         IssueType = "epic"
-	TypeChore        IssueType = "chore"
 	TypeMessage      IssueType = "message"       // Ephemeral communication between workers
 	TypeMergeRequest IssueType = "merge-request" // Merge queue entry for refinery processing
 	TypeMolecule     IssueType = "molecule"      // Template molecule for issue hierarchies
@@ -495,10 +502,12 @@ const (
 	TypeSlot         IssueType = "slot"          // Exclusive access slot (merge-slot gate)
 )
 
-// IsValid checks if the issue type value is valid
+// IsValid checks if the issue type is a core work type.
+// Only core work types (bug, feature, task, epic, chore) are built-in.
+// Other types (molecule, gate, convoy, etc.) require types.custom configuration.
 func (t IssueType) IsValid() bool {
 	switch t {
-	case TypeBug, TypeFeature, TypeTask, TypeEpic, TypeChore, TypeMessage, TypeMergeRequest, TypeMolecule, TypeGate, TypeAgent, TypeRole, TypeRig, TypeConvoy, TypeEvent, TypeSlot:
+	case TypeBug, TypeFeature, TypeTask, TypeEpic, TypeChore:
 		return true
 	}
 	return false
@@ -569,8 +578,7 @@ func (t IssueType) RequiredSections() []RequiredSection {
 			{Heading: "## Success Criteria", Hint: "Define high-level success criteria"},
 		}
 	default:
-		// Chore, message, molecule, gate, agent, role, convoy, event, merge-request
-		// have no required sections
+		// Chore and custom types have no required sections
 		return nil
 	}
 }

internal/types/types_test.go

@@ -539,20 +539,24 @@ func TestIssueTypeIsValid(t *testing.T) {
 		issueType IssueType
 		valid     bool
 	}{
+		// Core work types are always valid
 		{TypeBug, true},
 		{TypeFeature, true},
 		{TypeTask, true},
 		{TypeEpic, true},
 		{TypeChore, true},
-		{TypeMessage, true},
-		{TypeMergeRequest, true},
-		{TypeMolecule, true},
-		{TypeGate, true},
-		{TypeAgent, true},
-		{TypeRole, true},
-		{TypeConvoy, true},
-		{TypeEvent, true},
-		{TypeSlot, true},
+		// Gas Town types require types.custom configuration
+		{TypeMessage, false},
+		{TypeMergeRequest, false},
+		{TypeMolecule, false},
+		{TypeGate, false},
+		{TypeAgent, false},
+		{TypeRole, false},
+		{TypeConvoy, false},
+		{TypeEvent, false},
+		{TypeSlot, false},
+		{TypeRig, false},
+		// Invalid types
 		{IssueType("invalid"), false},
 		{IssueType(""), false},
 	}