memoryd: a match guard, not an if in the arm (clippy 1.95)

Clippy 1.95's collapsible_match flags the nested `if` in the
`LogRecord::User` arm of `index_record`, and the workspace pins
rust-version 1.95, so `make gate` failed on titan. An empty user message
now falls to the `_ => {}` arm, which indexes nothing, as before.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

crates/memoryd/src/index.rs

@@ -221,15 +221,13 @@ impl Index {
             return Ok(());
         }
         match record {
-            LogRecord::User { time, content } => {
-                if !content.trim().is_empty() {
-                    let src = Source {
-                        time: time.to_rfc3339(),
-                        role: "owner".to_string(),
-                        ..base.clone()
-                    };
-                    self.add(content, &src)?;
-                }
+            LogRecord::User { time, content } if !content.trim().is_empty() => {
+                let src = Source {
+                    time: time.to_rfc3339(),
+                    role: "owner".to_string(),
+                    ..base.clone()
+                };
+                self.add(content, &src)?;
             }
             LogRecord::Assistant {
                 time,