WIP: Rename context_new → context, delete old files, fix UI layer

Renamed context_new.rs to context.rs, deleted context_old.rs,
types.rs, openai.rs, parsing.rs. Updated all imports. Rewrote
user/context.rs and user/widgets.rs for new types. Stubbed
working_stack tool. Killed tokenize_conv_entry.

Remaining: mind/mod.rs, mind/dmn.rs, learn.rs, chat.rs,
subconscious.rs, oneshot.rs.

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

src/mind/log.rs

@@ -2,7 +2,7 @@ use anyhow::{Context, Result};
 use std::fs::{File, OpenOptions};
 use std::io::{BufRead, BufReader, Seek, SeekFrom, Write};
 use std::path::{Path, PathBuf};
-use crate::agent::context_new::AstNode;
+use crate::agent::context::AstNode;
 
 pub struct ConversationLog {
     path: PathBuf,