Delete ui_channel.rs — relocate types, remove all UiMessage/UiSender plumbing

Types relocated:
- StreamTarget → mind/mod.rs (Mind decides Conversation vs Autonomous)
- SharedActiveTools + shared_active_tools() → agent/tools/mod.rs
- ContextSection + SharedContextState → agent/context.rs (already there)
- StatusInfo + ContextInfo → user/mod.rs (UI display state)

Removed UiSender from: Agent::turn, Mind, learn.rs, all function signatures.
The entire message-passing layer is gone. All state flows through
Agent fields (activities, entries, streaming) read by the UI via try_lock.

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

src/user/mod.rs

@@ -8,7 +8,6 @@ pub mod context;
 pub mod subconscious;
 pub mod unconscious;
 pub mod thalamus;
-pub mod ui_channel;
 
 use anyhow::Result;
 use ratatui::crossterm::event::{Event, EventStream, KeyEventKind};
@@ -30,7 +29,33 @@ use ratatui::{
 };
 use std::io;
 
-use crate::user::ui_channel::{ContextInfo, SharedContextState, StatusInfo};
+use crate::agent::context::SharedContextState;
+
+/// Status info for the bottom status bar.
+#[derive(Debug, Clone)]
+pub struct StatusInfo {
+    pub dmn_state: String,
+    pub dmn_turns: u32,
+    pub dmn_max_turns: u32,
+    pub prompt_tokens: u32,
+    pub completion_tokens: u32,
+    pub model: String,
+    pub turn_tools: u32,
+    pub context_budget: String,
+}
+
+/// Context loading details for the debug screen.
+#[derive(Debug, Clone)]
+pub struct ContextInfo {
+    pub model: String,
+    pub available_models: Vec<String>,
+    pub prompt_file: String,
+    pub backend: String,
+    pub instruction_files: Vec<(String, usize)>,
+    pub memory_files: Vec<(String, usize)>,
+    pub system_prompt_chars: usize,
+    pub context_message_chars: usize,
+}
 
 /// Build the screen legend from screen labels.
 pub(crate) fn screen_legend_from(interact: &dyn ScreenView, screens: &[Box<dyn ScreenView>]) -> String {
@@ -100,7 +125,7 @@ pub struct App {
     pub temperature: f32,
     pub top_p: f32,
     pub top_k: u32,
-    pub(crate) active_tools: crate::user::ui_channel::SharedActiveTools,
+    pub(crate) active_tools: crate::agent::tools::SharedActiveTools,
     pub should_quit: bool,
     pub submitted: Vec<String>,
     pub hotkey_actions: Vec<HotkeyAction>,
@@ -112,7 +137,7 @@ pub struct App {
 }
 
 impl App {
-    pub fn new(model: String, shared_context: SharedContextState, active_tools: crate::user::ui_channel::SharedActiveTools) -> Self {
+    pub fn new(model: String, shared_context: SharedContextState, active_tools: crate::agent::tools::SharedActiveTools) -> Self {
         Self {
             status: StatusInfo {
                 dmn_state: "resting".into(), dmn_turns: 0, dmn_max_turns: 20,
@@ -189,11 +214,10 @@ pub async fn start(cli: crate::user::CliArgs) -> Result<()> {
         unsafe { std::env::set_var("POC_DEBUG", "1") };
     }
 
-    let (ui_tx, ui_rx) = ui_channel::channel();
     let (turn_tx, turn_rx) = tokio::sync::mpsc::channel(1);
     let (mind_tx, mind_rx) = tokio::sync::mpsc::unbounded_channel();
 
-    let mind = crate::mind::Mind::new(config, ui_tx.clone(), turn_tx);
+    let mind = crate::mind::Mind::new(config, turn_tx);
 
     let shared_context = mind.agent.lock().await.shared_context.clone();
     let shared_active_tools = mind.agent.lock().await.active_tools.clone();