arch: Add Gateway Architecture + crawler_gen_0 organism

Gateway Architecture (new):
- Unified tier model (Tier 0-5) for sensory routing
- Weight-based routing: node.weight determines processing tier
- Function Gemma as structured JSON boundary
- Separates routing from translation (vocabulary only at Tier 4)

crawler_gen_0 (new):
- First Virtual Garden organism specification
- Light-seeking cube with photoresistor
- Lifeforce economy: light = income, movement = cost

Updated documents with Gateway references:
- Endgame-Vision.md (v6.5)
- Cellular-Architecture.md (v4.3)
- Nervous-System.md
- Attention-Flow.md
- Message-Protocol-Design.md (Escalation Service = Gateway)
- Organisms-Index.md

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

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

architecture/organisms/Organisms-Index.md

@@ -32,6 +32,15 @@ How the hivemind learns, evolves, and resolves conflict.
 - Mount Olympus council mode (dafit + Chrysalis + Nyx)
 - **Status**: Core evolutionary dynamics
 
+### [crawler_gen_0.md](crawler_gen_0.md)
+The simplest organism — a cube that seeks light.
+- Virtual Garden training target
+- Single sensor: photoresistor on back
+- Single goal: move into light cone
+- Lifeforce economy: light = income, movement = cost
+- Foundation for all "seek resource" behaviors
+- **Status**: Design document, ready for implementation
+
 ---
 
 ## Planned Documents