Remove bd mol run - orchestration belongs in gt

bd mol run was a convenience combo (pour + assign + pin + start) that
felt like orchestration but lived in the data layer. This blurred the
architectural boundary between bd (data) and gt (orchestration).

- Delete cmd/bd/mol_run.go entirely
- Update mol.go help text to remove run reference
- Update mol_current.go to suggest bd pour instead

gt spawn will implement the orchestration combo by calling the atomic
bd commands (pour, update, pin) directly.

Closes bd-00u3

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

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

cmd/bd/mol_current.go

@@ -100,7 +100,7 @@ The output shows all steps with status indicators:
 				}
 				fmt.Println(".")
 				fmt.Println("\nTo start work on a molecule:")
-				fmt.Println("  bd mol run <proto-id>       # Spawn and start a new molecule")
+				fmt.Println("  bd pour <proto-id>          # Instantiate a molecule from template")
 				fmt.Println("  bd update <step-id> --status in_progress  # Claim a step")
 				return
 			}