agent: move oneshot execution from subconscious to agent module

Move agent execution machinery (run_one_agent, spawn_agent, PID
tracking) from subconscious/knowledge.rs to agent/oneshot.rs — the
agent module owns execution, subconscious owns scheduling and defs.

Delete subconscious/llm.rs — callers now use api::call_api_with_tools_sync
directly. Audit and compare inline the call; oneshot inlines tool
filtering.

Update all callers: consolidate, daemon, subconscious, cli/agent.

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

src/lib.rs

@@ -82,7 +82,7 @@ pub use hippocampus::query::parser as query_parser;
 
 pub use subconscious as agents;
 pub use subconscious::{
-    llm, audit, consolidate, knowledge,
+    audit, consolidate,
     digest, daemon,
 };
 // Backward compat: memory_search moved from subconscious::hook to claude::hook