refactor(mol): remove bd mol spawn - use pour/wisp only (bd-8y9t)

Remove the spawn command from bd mol. Proto instantiation now uses:
- bd pour <proto> - Instantiate as persistent mol (liquid phase)
- bd wisp create <proto> - Instantiate as ephemeral wisp (vapor phase)

Rationale:
- 'spawn' doesn't fit the chemistry metaphor
- Two phase transitions (pour/wisp) are clearer than one command with flags
- Avoids confusion about defaults

Changes:
- Delete mol_spawn.go
- Update mol.go, mol_catalog.go, mol_distill.go to reference pour/wisp
- Update pour.go and wisp.go to remove 'Equivalent to spawn' comments
- Update info.go changelog entries
- Update CHANGELOG.md, ARCHITECTURE.md, DELETIONS.md

Closes bd-8y9t

cmd/bd/wisp.go

@@ -93,8 +93,6 @@ The wisp will:
   - NOT sync to remote
   - Either evaporate (burn) or condense to digest (squash)
 
-Equivalent to: bd mol spawn <proto>
-
 Examples:
   bd wisp create mol-patrol                    # Ephemeral patrol cycle
   bd wisp create mol-health-check              # One-time health check