feat: extract Gas Town types from beads core (bd-i54l)

Remove Gas Town-specific issue types (agent, role, rig, convoy, slot)
from beads core. These types are now identified by labels instead:
- gt:agent, gt:role, gt:rig, gt:convoy, gt:slot

Changes:
- internal/types/types.go: Remove TypeAgent, TypeRole, TypeRig, TypeConvoy, TypeSlot constants
- cmd/bd/agent.go: Create agents with TypeTask + gt:agent label
- cmd/bd/merge_slot.go: Create slots with TypeTask + gt:slot label
- internal/storage/sqlite/queries.go, transaction.go: Query convoys by gt:convoy label
- internal/rpc/server_issues_epics.go: Check gt:agent label for role_type/rig label auto-add
- cmd/bd/create.go: Check gt:agent label for role_type/rig label auto-add
- internal/ui/styles.go: Remove agent/role/rig type colors
- cmd/bd/export_obsidian.go: Remove agent/role/rig/convoy type tag mappings
- Update all affected tests

This enables beads to be a generic issue tracker while Gas Town
uses labels for its specific type semantics.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Executed-By: beads/crew/dave
Rig: beads
Role: crew

internal/ui/styles.go

@@ -135,18 +135,8 @@ var (
 		Light: "", // standard text color
 		Dark:  "",
 	}
-	ColorTypeAgent = lipgloss.AdaptiveColor{
-		Light: "#59c2ff", // cyan - agent identity
-		Dark:  "#59c2ff",
-	}
-	ColorTypeRole = lipgloss.AdaptiveColor{
-		Light: "#7fd962", // green - role definition
-		Dark:  "#7fd962",
-	}
-	ColorTypeRig = lipgloss.AdaptiveColor{
-		Light: "#e6a756", // orange - rig identity (project container)
-		Dark:  "#e6a756",
-	}
+	// Note: Gas Town-specific types (agent, role, rig) have been removed.
+	// Use labels (gt:agent, gt:role, gt:rig) with custom styling if needed.
 
 	// === Issue ID Color ===
 	// IDs use standard text color - subtle, not attention-grabbing
@@ -194,9 +184,7 @@ var (
 	TypeTaskStyle    = lipgloss.NewStyle().Foreground(ColorTypeTask)
 	TypeEpicStyle    = lipgloss.NewStyle().Foreground(ColorTypeEpic)
 	TypeChoreStyle   = lipgloss.NewStyle().Foreground(ColorTypeChore)
-	TypeAgentStyle   = lipgloss.NewStyle().Foreground(ColorTypeAgent)
-	TypeRoleStyle    = lipgloss.NewStyle().Foreground(ColorTypeRole)
-	TypeRigStyle     = lipgloss.NewStyle().Foreground(ColorTypeRig)
+	// Note: Gas Town-specific type styles (agent, role, rig) have been removed.
 )
 
 // CategoryStyle for section headers - bold with accent color
@@ -331,7 +319,8 @@ func RenderPriority(priority int) string {
 }
 
 // RenderType renders an issue type with semantic styling
-// bugs get color; all other types use standard text
+// bugs and epics get color; all other types use standard text
+// Note: Gas Town-specific types (agent, role, rig) now fall through to default
 func RenderType(issueType string) string {
 	switch issueType {
 	case "bug":
@@ -344,12 +333,6 @@ func RenderType(issueType string) string {
 		return TypeEpicStyle.Render(issueType)
 	case "chore":
 		return TypeChoreStyle.Render(issueType)
-	case "agent":
-		return TypeAgentStyle.Render(issueType)
-	case "role":
-		return TypeRoleStyle.Render(issueType)
-	case "rig":
-		return TypeRigStyle.Render(issueType)
 	default:
 		return issueType
 	}

internal/ui/styles_test.go

@@ -92,9 +92,10 @@ func TestRenderTypeVariants(t *testing.T) {
 		{"task", TypeTaskStyle.Render("task")},
 		{"epic", TypeEpicStyle.Render("epic")},
 		{"chore", TypeChoreStyle.Render("chore")},
-		{"agent", TypeAgentStyle.Render("agent")},
-		{"role", TypeRoleStyle.Render("role")},
-		{"rig", TypeRigStyle.Render("rig")},
+		// Gas Town types (agent, role, rig) have been removed - they now fall through to default
+		{"agent", "agent"},  // Falls through to default (no styling)
+		{"role", "role"},    // Falls through to default (no styling)
+		{"rig", "rig"},      // Falls through to default (no styling)
 		{"custom", "custom"},
 	}
 	for _, tc := range cases {