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/agent/mod.rs

@@ -28,7 +28,8 @@ use context::{ConversationEntry, ContextState, ContextBudget};
 use tools::{summarize_args, working_stack};
 
 use crate::mind::log::ConversationLog;
-use crate::user::ui_channel::{ContextSection, SharedContextState, StreamTarget, UiSender};
+use crate::agent::context::{ContextSection, SharedContextState};
+use crate::mind::StreamTarget;
 use crate::subconscious::learn;
 
 // --- Activity tracking (RAII guards) ---
@@ -177,7 +178,7 @@ pub struct Agent {
     /// TODO: move to Session — it's session-level, not agent-level.
     pub agent_cycles: crate::subconscious::subconscious::AgentCycleState,
     /// Shared active tools — Agent writes, TUI reads.
-    pub active_tools: crate::user::ui_channel::SharedActiveTools,
+    pub active_tools: crate::agent::tools::SharedActiveTools,
 }
 
 fn render_journal(entries: &[context::JournalEntry]) -> String {
@@ -199,7 +200,7 @@ impl Agent {
         prompt_file: String,
         conversation_log: Option<ConversationLog>,
         shared_context: SharedContextState,
-        active_tools: crate::user::ui_channel::SharedActiveTools,
+        active_tools: tools::SharedActiveTools,
     ) -> Self {
         let tokenizer = tiktoken_rs::cl100k_base()
             .expect("failed to load cl100k_base tokenizer");
@@ -325,7 +326,6 @@ impl Agent {
     pub async fn turn(
         agent: Arc<tokio::sync::Mutex<Agent>>,
         user_input: &str,
-        ui_tx: &UiSender,
         target: StreamTarget,
     ) -> Result<TurnResult> {
         // --- Pre-loop setup (lock 1): agent cycle, memories, user input ---
@@ -382,7 +382,7 @@ impl Agent {
                 let mut me = agent.lock().await;
                 let mut bg_ds = DispatchState::new();
                 for (call, output) in bg_results {
-                    me.apply_tool_result(&call, output, ui_tx, &mut bg_ds);
+                    me.apply_tool_result(&call, output, &mut bg_ds);
                 }
                 me.push_message(Message::user(user_input));
             }
@@ -408,7 +408,6 @@ impl Agent {
                 me.client.start_stream(
                     &api_messages,
                     &me.tools,
-                    ui_tx,
                     &me.reasoning_effort,
                     sampling,
                     None,
@@ -522,7 +521,7 @@ impl Agent {
                 // Reacquire to apply results
                 let mut me = agent.lock().await;
                 for (call, output) in results {
-                    me.apply_tool_result(&call, output, ui_tx, &mut ds);
+                    me.apply_tool_result(&call, output, &mut ds);
                 }
                 me.publish_context_state();
                 continue;
@@ -536,7 +535,7 @@ impl Agent {
                     // Drop lock before tool dispatch
                     for call in &calls {
                         Agent::dispatch_tool_call_unlocked(
-                            &agent, &active_tools, call, ui_tx, &mut ds,
+                            &agent, &active_tools, call, &mut ds,
                         ).await;
                     }
                     continue;
@@ -568,9 +567,8 @@ impl Agent {
     /// Used by `turn()` which manages its own locking.
     async fn dispatch_tool_call_unlocked(
         agent: &Arc<tokio::sync::Mutex<Agent>>,
-        active_tools: &crate::user::ui_channel::SharedActiveTools,
+        active_tools: &crate::agent::tools::SharedActiveTools,
         call: &ToolCall,
-        ui_tx: &UiSender,
         ds: &mut DispatchState,
     ) {
         let args: serde_json::Value = match serde_json::from_str(&call.function.arguments) {
@@ -579,7 +577,7 @@ impl Agent {
                 let err = format!("Error: malformed tool call arguments: {e}");
                 let _act = start_activity(agent, format!("rejected: {} (bad args)", call.function.name)).await;
                 let mut me = agent.lock().await;
-                me.apply_tool_result(call, err, ui_tx, ds);
+                me.apply_tool_result(call, err, ds);
                 return;
             }
         };
@@ -613,7 +611,7 @@ impl Agent {
         if let Ok((call, output)) = entry.handle.await {
             // Brief lock to apply result
             let mut me = agent.lock().await;
-            me.apply_tool_result(&call, output, ui_tx, ds);
+            me.apply_tool_result(&call, output, ds);
         }
     }
 
@@ -622,7 +620,6 @@ impl Agent {
         &mut self,
         call: &ToolCall,
         output: String,
-        ui_tx: &UiSender,
         ds: &mut DispatchState,
     ) {
         let args: serde_json::Value =