feat(mol): add compound visualization in bd mol show (bd-iw4z)

Add visualization for compound molecules (those created by bonding protos):

- Detect compound molecules via IsCompound() check on root issue
- Display "Bonded from:" section showing constituent protos with bond types
- Show bond point when specified (attachment site within molecule)
- Format bond types as human-readable: sequential, parallel, on-failure, root
- Include is_compound and bonded_from in JSON output

Example output for compound molecules:
  🧪 Compound: proto-feature-with-tests
     ID: bd-abc123
     Steps: 5

  🔗 Bonded from:
     ├── proto-feature (sequential)
     └── proto-testing (sequential, at step-2)

Added unit tests for compound detection and bond type formatting.

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

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

cmd/bd/mol_show.go

@@ -70,14 +70,27 @@ func showMolecule(subgraph *MoleculeSubgraph) {
 			"issues":       subgraph.Issues,
 			"dependencies": subgraph.Dependencies,
 			"variables":    extractAllVariables(subgraph),
+			"is_compound":  subgraph.Root.IsCompound(),
+			"bonded_from":  subgraph.Root.BondedFrom,
 		})
 		return
 	}
 
-	fmt.Printf("\n%s Molecule: %s\n", ui.RenderAccent("🧪"), subgraph.Root.Title)
+	// Determine molecule type label
+	moleculeType := "Molecule"
+	if subgraph.Root.IsCompound() {
+		moleculeType = "Compound"
+	}
+
+	fmt.Printf("\n%s %s: %s\n", ui.RenderAccent("🧪"), moleculeType, subgraph.Root.Title)
 	fmt.Printf("   ID: %s\n", subgraph.Root.ID)
 	fmt.Printf("   Steps: %d\n", len(subgraph.Issues))
 
+	// Show compound bonding info if this is a compound molecule
+	if subgraph.Root.IsCompound() {
+		showCompoundBondingInfo(subgraph.Root)
+	}
+
 	vars := extractAllVariables(subgraph)
 	if len(vars) > 0 {
 		fmt.Printf("\n%s Variables:\n", ui.RenderWarn("📝"))
@@ -91,6 +104,52 @@ func showMolecule(subgraph *MoleculeSubgraph) {
 	fmt.Println()
 }
 
+// showCompoundBondingInfo displays the bonding lineage for compound molecules
+func showCompoundBondingInfo(root *types.Issue) {
+	if !root.IsCompound() {
+		return
+	}
+
+	constituents := root.GetConstituents()
+	fmt.Printf("\n%s Bonded from:\n", ui.RenderAccent("🔗"))
+
+	for i, ref := range constituents {
+		connector := "├──"
+		if i == len(constituents)-1 {
+			connector = "└──"
+		}
+
+		// Format bond type for display
+		bondTypeDisplay := formatBondType(ref.BondType)
+
+		// Show source ID with bond type
+		if ref.BondPoint != "" {
+			fmt.Printf("   %s %s (%s, at %s)\n", connector, ref.SourceID, bondTypeDisplay, ref.BondPoint)
+		} else {
+			fmt.Printf("   %s %s (%s)\n", connector, ref.SourceID, bondTypeDisplay)
+		}
+	}
+}
+
+// formatBondType returns a human-readable bond type description
+func formatBondType(bondType string) string {
+	switch bondType {
+	case types.BondTypeSequential:
+		return "sequential"
+	case types.BondTypeParallel:
+		return "parallel"
+	case types.BondTypeConditional:
+		return "on-failure"
+	case types.BondTypeRoot:
+		return "root"
+	default:
+		if bondType == "" {
+			return "default"
+		}
+		return bondType
+	}
+}
+
 // ParallelInfo holds parallel analysis information for a step
 type ParallelInfo struct {
 	StepID        string   `json:"step_id"`
@@ -327,14 +386,27 @@ func showMoleculeWithParallel(subgraph *MoleculeSubgraph) {
 			"dependencies": subgraph.Dependencies,
 			"variables":    extractAllVariables(subgraph),
 			"parallel":     analysis,
+			"is_compound":  subgraph.Root.IsCompound(),
+			"bonded_from":  subgraph.Root.BondedFrom,
 		})
 		return
 	}
 
-	fmt.Printf("\n%s Molecule: %s\n", ui.RenderAccent("🧪"), subgraph.Root.Title)
+	// Determine molecule type label
+	moleculeType := "Molecule"
+	if subgraph.Root.IsCompound() {
+		moleculeType = "Compound"
+	}
+
+	fmt.Printf("\n%s %s: %s\n", ui.RenderAccent("🧪"), moleculeType, subgraph.Root.Title)
 	fmt.Printf("   ID: %s\n", subgraph.Root.ID)
 	fmt.Printf("   Steps: %d (%d ready)\n", analysis.TotalSteps, analysis.ReadySteps)
 
+	// Show compound bonding info if this is a compound molecule
+	if subgraph.Root.IsCompound() {
+		showCompoundBondingInfo(subgraph.Root)
+	}
+
 	// Show parallel groups summary
 	if len(analysis.ParallelGroups) > 0 {
 		fmt.Printf("\n%s Parallel Groups:\n", ui.RenderPass("⚡"))