fix(clippy): Rust 1.95 compatibility — sort_by_key + collapsible_match

CI runs on stable Rust which advanced from 1.93 to 1.95, introducing
two newly-enforced lints under -D warnings:

- clippy::unnecessary_sort_by (12 sites) — rewrite sort_by closures
  that only call .cmp on Copy keys as sort_by_key, using std::cmp::Reverse
  for the descending ones.
- clippy::collapsible_match (1 site) — merge the MemoryState::Dormant
  inner if into a match guard. The equivalent rewrite for the Ping/Pong
  arm in websocket.rs is blocked by a move of non-Copy Bytes across the
  match-guard boundary, so that one site gets an explicit #[allow].

Files touched:
- crates/vestige-core/src/advanced/{chains,compression,cross_project,reconsolidation}.rs
- crates/vestige-core/src/codebase/{git,relationships}.rs
- crates/vestige-core/src/neuroscience/{importance_signals,memory_states,predictive_retrieval}.rs
- crates/vestige-mcp/src/tools/{changelog,cross_reference}.rs
- crates/vestige-mcp/src/dashboard/websocket.rs

Verified: cargo clippy --workspace -- -D warnings green on rustc 1.95.0;
cargo test --workspace unchanged (1292 tests green).

crates/vestige-core/src/advanced/chains.rs

@@ -333,7 +333,7 @@ impl MemoryChainBuilder {
 
         // Sort by frequency
         let mut bridge_list: Vec<_> = bridges.into_iter().collect();
-        bridge_list.sort_by(|a, b| b.1.cmp(&a.1));
+        bridge_list.sort_by_key(|b| std::cmp::Reverse(b.1));
 
         bridge_list.into_iter().map(|(id, _)| id).collect()
     }

crates/vestige-core/src/advanced/compression.rs

@@ -298,7 +298,7 @@ impl MemoryCompressor {
 
         // Sort by age (oldest first)
         let mut sorted: Vec<_> = memories.iter().collect();
-        sorted.sort_by(|a, b| a.created_at.cmp(&b.created_at));
+        sorted.sort_by_key(|a| a.created_at);
 
         for memory in sorted {
             if assigned.contains(&memory.id) {

crates/vestige-core/src/advanced/cross_project.rs

@@ -417,7 +417,7 @@ impl CrossProjectLearner {
             }
         }
 
-        suggestions.sort_by(|a, b| b.priority.cmp(&a.priority));
+        suggestions.sort_by_key(|b| std::cmp::Reverse(b.priority));
         suggestions
     }
 

crates/vestige-core/src/advanced/reconsolidation.rs

@@ -678,7 +678,7 @@ impl ReconsolidationManager {
             .read()
             .map(|history| {
                 let mut recent: Vec<_> = history.iter().cloned().collect();
-                recent.sort_by(|a, b| b.retrieved_at.cmp(&a.retrieved_at));
+                recent.sort_by_key(|b| std::cmp::Reverse(b.retrieved_at));
                 recent.into_iter().take(limit).collect()
             })
             .unwrap_or_default()

crates/vestige-core/src/codebase/git.rs

@@ -673,11 +673,11 @@ impl GitAnalyzer {
 
         // Top contributors
         let mut top_contributors: Vec<_> = author_counts.into_iter().collect();
-        top_contributors.sort_by(|a, b| b.1.cmp(&a.1));
+        top_contributors.sort_by_key(|b| std::cmp::Reverse(b.1));
 
         // Hot files (most frequently changed)
         let mut hot_files: Vec<_> = file_counts.into_iter().collect();
-        hot_files.sort_by(|a, b| b.1.cmp(&a.1));
+        hot_files.sort_by_key(|b| std::cmp::Reverse(b.1));
 
         Ok(HistoryAnalysis {
             bug_fixes,

crates/vestige-core/src/codebase/relationships.rs

@@ -579,7 +579,7 @@ impl RelationshipTracker {
         }
 
         let mut sorted: Vec<_> = file_degrees.into_iter().collect();
-        sorted.sort_by(|a, b| b.1.cmp(&a.1));
+        sorted.sort_by_key(|b| std::cmp::Reverse(b.1));
         sorted.truncate(limit);
 
         sorted

crates/vestige-core/src/neuroscience/importance_signals.rs

@@ -464,7 +464,7 @@ impl PredictionModel {
             .filter_map(|ng| patterns.get(&ng).map(|&count| (ng, count)))
             .collect();
 
-        familiar.sort_by(|a, b| b.1.cmp(&a.1));
+        familiar.sort_by_key(|b| std::cmp::Reverse(b.1));
         familiar.into_iter().take(5).map(|(ng, _)| ng).collect()
     }
 
@@ -489,7 +489,7 @@ impl PredictionModel {
     fn apply_decay(&self, patterns: &mut HashMap<String, u32>) {
         // Remove lowest frequency patterns
         let mut entries: Vec<_> = patterns.iter().map(|(k, v)| (k.clone(), *v)).collect();
-        entries.sort_by(|a, b| a.1.cmp(&b.1));
+        entries.sort_by_key(|a| a.1);
 
         // Remove bottom 20%
         let remove_count = patterns.len() / 5;

crates/vestige-core/src/neuroscience/memory_states.rs

@@ -1276,14 +1276,12 @@ impl MemoryStateInfo {
                     ));
                 }
             }
-            MemoryState::Dormant => {
-                if duration_since_access.num_days() > 20 {
-                    recommendations.push(
-                        "Consider accessing this memory soon to prevent it from \
-                         becoming harder to retrieve."
-                            .to_string(),
-                    );
-                }
+            MemoryState::Dormant if duration_since_access.num_days() > 20 => {
+                recommendations.push(
+                    "Consider accessing this memory soon to prevent it from \
+                     becoming harder to retrieve."
+                        .to_string(),
+                );
             }
             _ => {}
         }

crates/vestige-core/src/neuroscience/predictive_retrieval.rs

@@ -582,7 +582,7 @@ impl UserModel {
         }
 
         // Sort by count and keep top patterns
-        patterns.sort_by(|a, b| b.1.cmp(&a.1));
+        patterns.sort_by_key(|b| std::cmp::Reverse(b.1));
         patterns.truncate(50);
     }
 

crates/vestige-mcp/src/dashboard/websocket.rs

@@ -123,6 +123,9 @@ async fn handle_socket(socket: WebSocket, state: AppState) {
             msg = receiver.next() => {
                 match msg {
                     Some(Ok(Message::Close(_))) | None => break,
+                    // Match guards can't move out of the bound `data` (Bytes is
+                    // not Copy), so the nested `if` is required here.
+                    #[allow(clippy::collapsible_match, clippy::collapsible_if)]
                     Some(Ok(Message::Ping(data))) => {
                         if sender.send(Message::Pong(data)).await.is_err() {
                             break;

crates/vestige-mcp/src/tools/changelog.rs

@@ -237,7 +237,7 @@ fn execute_system_wide(
     }
 
     // Sort by timestamp descending
-    events.sort_by(|a, b| b.0.cmp(&a.0));
+    events.sort_by_key(|b| std::cmp::Reverse(b.0));
 
     // Truncate to limit
     events.truncate(limit as usize);

crates/vestige-mcp/src/tools/cross_reference.rs

@@ -560,7 +560,7 @@ pub async fn execute(
 
     // Sort by date descending for supersession
     let mut by_date = scored.iter().collect::<Vec<_>>();
-    by_date.sort_by(|a, b| b.updated_at.cmp(&a.updated_at));
+    by_date.sort_by_key(|b| std::cmp::Reverse(b.updated_at));
 
     for i in 0..by_date.len() {
         for j in (i + 1)..by_date.len() {