Rename agent/ to user/ and poc-agent binary to consciousness

Mechanical rename: src/agent/ -> src/user/, all crate::agent:: ->
crate::user:: references updated. Binary poc-agent renamed to
consciousness with CLI name and user-facing strings updated.

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

src/lib.rs

@@ -3,7 +3,7 @@
 // thought/       — shared cognitive substrate (tools, context, memory ops)
 // hippocampus/   — memory storage, retrieval, consolidation
 // subconscious/  — autonomous agents (reflect, surface, consolidate, ...)
-// agent/         — interactive agent (TUI, tools, API clients)
+// user/          — interactive agent (TUI, tools, API clients)
 
 /// Debug logging macro — writes to ~/.consciousness/logs/debug.log
 #[macro_export]
@@ -24,7 +24,7 @@ macro_rules! dbglog {
 }
 
 // Agent infrastructure
-pub mod agent;
+pub mod user;
 
 // Shared cognitive infrastructure — used by both agent and subconscious
 pub mod thought;