enrich: fix dedup keys never written for empty mining results

The early return on line 343 when the LLM found no missed experiences
bypassed the dedup key writes at lines 397-414, despite the comment
saying "even if count == 0, to prevent re-runs." This caused sessions
with nothing to mine to be re-mined every 60s tick indefinitely.

Fix: replace the early return with a conditional print, so the dedup
keys are always written and saved.

src/enrich.rs

@@ -340,10 +340,9 @@ pub fn experience_mine(
 
     if entries.is_empty() {
         println!("  No missed experiences found.");
-        return Ok(0);
+    } else {
+        println!("  Found {} experiential moments:", entries.len());
     }
-
-    println!("  Found {} experiential moments:", entries.len());
     let mut count = 0;
     for entry in &entries {
         let ts = entry.get("timestamp").and_then(|v| v.as_str()).unwrap_or("");