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

docs/ARCHITECTURE.md

@@ -273,12 +273,12 @@ open ──▶ in_progress ──▶ closed
 
 ```
 ┌─────────────────┐    ┌─────────────────┐    ┌─────────────────┐
-│   bd mol spawn  │───▶│  Wisp Issues    │───▶│  bd mol squash  │
-│   (from template)│    │  (local-only)   │    │  (→ digest)     │
+│ bd wisp create  │───▶│  Wisp Issues    │───▶│  bd mol squash  │
+│ (from template) │    │  (local-only)   │    │  (→ digest)     │
 └─────────────────┘    └─────────────────┘    └─────────────────┘
 ```
 
-1. **Spawn:** Create wisps from a molecule template
+1. **Create:** Create wisps from a molecule template
 2. **Execute:** Agent works through wisp steps (local SQLite only)
 3. **Squash:** Compress wisps into a permanent digest issue