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

@@ -221,8 +221,7 @@ impl Index {
             return Ok(());
         }
         match record {
-            LogRecord::User { time, content } => {
+            LogRecord::User { time, content } if !content.trim().is_empty() => {
-                if !content.trim().is_empty() {
                 let src = Source {
                     time: time.to_rfc3339(),
                     role: "owner".to_string(),
@@ -230,7 +229,6 @@ impl Index {
                 };
                 self.add(content, &src)?;
             }
-            }
             LogRecord::Assistant {
                 time,
                 content,