Restore full N×M memory scoring matrix (/score command)

The full matrix scorer was deleted during the AST conversion. Restore
it: /score runs score_memories() which computes divergence for every
memory × response pair, stores the MemoryScore on MindState, and
displays per-memory weights with bar charts on the F2 screen.

Both scoring paths now use ActivityGuard::update() for live progress
in the status bar instead of creating a new activity per iteration.

Also bumps score API timeout from 120s to 300s and adds progress
logging throughout.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

src/agent/context.rs

@@ -93,7 +93,14 @@ impl<'de> Deserialize<'de> for NodeLeaf {
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub enum AstNode {
     Leaf(NodeLeaf),
-    Branch { role: Role, children: Vec<AstNode> },
+    Branch {
+        role: Role,
+        children: Vec<AstNode>,
+        /// Per-response memory attribution from full scoring matrix.
+        /// Maps memory key → divergence score for this response.
+        #[serde(default, skip_serializing_if = "std::collections::BTreeMap::is_empty")]
+        memory_scores: std::collections::BTreeMap<String, f64>,
+    },
 }
 
 /// The context window: four sections as Vec<AstNode>.
@@ -277,13 +284,14 @@ impl AstNode {
     // -- Branch constructors --------------------------------------------------
 
     pub fn branch(role: Role, children: Vec<AstNode>) -> Self {
-        Self::Branch { role, children }
+        Self::Branch { role, children, memory_scores: Default::default() }
     }
 
     pub fn system_msg(text: impl Into<String>) -> Self {
         Self::Branch {
             role: Role::System,
             children: vec![Self::content(text)],
+            memory_scores: Default::default(),
         }
     }
 
@@ -291,6 +299,7 @@ impl AstNode {
         Self::Branch {
             role: Role::User,
             children: vec![Self::content(text)],
+            memory_scores: Default::default(),
         }
     }
 
@@ -306,9 +315,10 @@ impl AstNode {
                 };
                 Self::Leaf(NodeLeaf { token_ids, ..leaf })
             }
-            Self::Branch { role, children } => Self::Branch {
+            Self::Branch { role, children, memory_scores, .. } => Self::Branch {
                 role,
                 children: children.into_iter().map(|c| c.retokenize()).collect(),
+                memory_scores,
             },
         }
     }
@@ -339,7 +349,7 @@ impl AstNode {
     pub fn label(&self) -> String {
         let cfg = crate::config::get();
         match self {
-            Self::Branch { role, children } => {
+            Self::Branch { role, children, .. } => {
                 let preview = children.first()
                     .and_then(|c| c.leaf())
                     .map(|l| truncate_preview(l.body.text(), 60))
@@ -370,7 +380,7 @@ impl AstNode {
     fn render_into(&self, out: &mut String) {
         match self {
             Self::Leaf(leaf) => leaf.body.render_into(out),
-            Self::Branch { role, children } => {
+            Self::Branch { role, children, .. } => {
                 out.push_str(&format!("<|im_start|>{}\n", role.as_str()));
                 for child in children {
                     child.render_into(out);
@@ -383,7 +393,7 @@ impl AstNode {
     fn token_ids_into(&self, out: &mut Vec<u32>) {
         match self {
             Self::Leaf(leaf) => out.extend_from_slice(&leaf.token_ids),
-            Self::Branch { role, children } => {
+            Self::Branch { role, children, .. } => {
                 out.push(tokenizer::IM_START);
                 out.extend(tokenizer::encode(&format!("{}\n", role.as_str())));
                 for child in children {
@@ -412,7 +422,7 @@ impl Ast for AstNode {
     fn tokens(&self) -> usize {
         match self {
             Self::Leaf(leaf) => leaf.tokens(),
-            Self::Branch { role, children } => {
+            Self::Branch { role, children, .. } => {
                 1 + tokenizer::encode(&format!("{}\n", role.as_str())).len()
                     + children.iter().map(|c| c.tokens()).sum::<usize>()
                     + 1 + tokenizer::encode("\n").len()
@@ -752,6 +762,7 @@ impl ContextState {
     pub fn identity(&self) -> &[AstNode]     { &self.identity }
     pub fn journal(&self) -> &[AstNode]      { &self.journal }
     pub fn conversation(&self) -> &[AstNode] { &self.conversation }
+    pub fn conversation_mut(&mut self) -> &mut Vec<AstNode> { &mut self.conversation }
 
     fn sections(&self) -> [&Vec<AstNode>; 4] {
         [&self.system, &self.identity, &self.journal, &self.conversation]