subconscious: move install_hook() from daemon.rs to hook.rs

The install_hook() function is about hook infrastructure setup, not daemon
runtime. Move it to hook.rs where it belongs alongside the hook execution
logic.

- Move install_hook() from daemon.rs to hook.rs
- Update caller in daemon.rs to use crate::subconscious:🪝:install_hook()
- Update caller in cli/admin.rs to use crate::subconscious:🪝:install_hook()

This improves module boundaries: daemon.rs now only contains daemon runtime
and admin commands, while hook.rs contains all hook-related functionality.

src/cli/admin.rs

@@ -40,7 +40,7 @@ pub fn cmd_init() -> Result<(), String> {
     println!("Indexed {} memory units", count);
 
     // Install hooks
-    crate::daemon::install_hook()?;
+    crate::subconscious::hook::install_hook()?;
 
     // Create config if none exists
     let config_path = std::env::var("POC_MEMORY_CONFIG")