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/user/widgets.rs

@@ -8,10 +8,8 @@ use ratatui::{
     Frame,
     crossterm::event::KeyCode,
 };
-use crate::agent::context::{ContextSection, ConversationEntry};
+use crate::agent::context::{AstNode, NodeBody, Ast};
 
-/// UI-only tree node for the section tree display.
-/// Built from ContextSection data; not used for budgeting.
 #[derive(Debug, Clone)]
 pub struct SectionView {
     pub name: String,
@@ -22,26 +20,30 @@ pub struct SectionView {
     pub status: String,
 }
 
-/// Build a SectionView tree from a ContextSection.
-/// Each entry becomes a child with label + expandable content.
-pub fn section_to_view(section: &ContextSection) -> SectionView {
-    let children: Vec<SectionView> = section.entries().iter().map(|ce| {
-        let content = match &ce.entry {
-            ConversationEntry::Log(_) => String::new(),
-            ConversationEntry::Thinking(text) => text.clone(),
-            _ => ce.entry.message().content_text().to_string(),
+pub fn section_to_view(name: &str, nodes: &[AstNode]) -> SectionView {
+    let children: Vec<SectionView> = nodes.iter().map(|node| {
+        let content = match node.leaf().map(|l| l.body()) {
+            Some(NodeBody::Log(_)) => String::new(),
+            Some(body) => body.text().to_string(),
+            None => node.children().iter()
+                .filter_map(|c| c.leaf())
+                .filter(|l| matches!(l.body(), NodeBody::Content(_)))
+                .map(|l| l.body().text())
+                .collect::<Vec<_>>()
+                .join(""),
         };
         SectionView {
-            name: ce.entry.label(),
-            tokens: ce.tokens(),
+            name: node.label(),
+            tokens: node.tokens(),
             content,
             children: Vec::new(),
             status: String::new(),
         }
     }).collect();
+    let total_tokens: usize = nodes.iter().map(|n| n.tokens()).sum();
     SectionView {
-        name: section.name.clone(),
-        tokens: section.tokens(),
+        name: name.to_string(),
+        tokens: total_tokens,
         content: String::new(),
         children,
         status: String::new(),