docs(volume): 🔥 consolidate VOLUME_DIRECTION.md into CONTRACT_VOLUME.md

docs/ARCH_INDEX.md

@@ -30,7 +30,6 @@ Plans, contracts, and research notes. Contracts define **system behavior**.
 
 - `IMPLEMENTATION_PLAN.md` — contract-first, phased implementation plan
 - `V1_READINESS.md` — v1.0 release criteria and dogfooding evidence
-- `VOLUME_DIRECTION.md` — product direction for the Dataset + Volume dual-paradigm model
 - `contracts/CONTRACT_CORE.md` — core model invariants and immutability
 - `contracts/CONTRACT_WRITE_API.md` — write API semantics and errors
 - `contracts/CONTRACT_STORAGE.md` — storage adapter obligations

docs/contracts/CONTRACT_VOLUME.md

@@ -305,10 +305,16 @@ volumes/<volume_id>/data/<offset>-<length>.bin
 
 - Dataset streaming: atomic construction of complete objects
 - Volume streaming: incremental commitment of partial truth
+- Neither is a wrapper or special case of the other
 
 If a workflow requires sparse, resumable, out-of-order, or range-verified truth,
 it belongs to `Volume`, not `Dataset`.
 
+Design discipline:
+- Adapters remain minimal; lifecycle semantics stay in Lode core.
+- Runtime-aware policy (scheduling, peer management, execution strategy)
+  belongs in consuming systems, not in Lode.
+
 ---
 
 ## Prohibited Behaviors