cleanup: remove dead migrate module, fix stale comment

migrate.rs was a one-time markdown→capnp conversion that's long done.
Remove it and update the identity.rs comment to reference the new
~/.consciousness/ path.

src/agent/identity.rs

@@ -69,7 +69,7 @@ fn find_context_files(cwd: &Path, prompt_file: &str) -> Vec<PathBuf> {
 /// For file sources, checks:
 ///   1. ~/.config/poc-agent/ (primary config dir)
 ///   2. Project dir (if set)
-///   3. Global (~/.claude/memory/)
+///   3. Global (~/.consciousness/)
 /// For journal source, loads recent journal entries.
 fn load_memory_files(cwd: &Path, memory_project: Option<&Path>, context_groups: &[ContextGroup]) -> Vec<(String, String)> {
     let home = match dirs::home_dir() {