Split hook.rs: core orchestration -> subconscious.rs

subconscious::subconscious — AgentCycleState, AgentInfo, AgentSnapshot,
  SavedAgentState, format_agent_output, cycle methods. Core agent
  lifecycle independent of Claude Code.

subconscious::hook — Claude Code hook: context loading, chunking,
  seen-set management, run_agent_cycles (serialized state entry point).

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

src/subconscious/mod.rs

@@ -16,6 +16,7 @@
 //   hook         — session hook: context injection, agent orchestration
 //   transcript   — shared JSONL transcript parsing
 
+pub mod subconscious;
 pub mod hook;
 pub mod transcript;
 pub mod api;