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/user/subconscious.rs

@@ -187,10 +187,9 @@ impl SubconsciousScreen {
         agent.context.try_lock().ok()
             .map(|ctx| {
                 let conv = ctx.conversation();
-                let mut view = section_to_view("Conversation", conv);
+                let view = section_to_view("Conversation", conv);
                 let fork = fork_point.min(view.children.len());
-                view.children = view.children.split_off(fork);
-                vec![view]
+                view.children.into_iter().skip(fork).collect()
             })
             .unwrap_or_default()
     }