review: a memory write wakes the Honcho worker

A write, an undo or an accepted write decided into the ledger waited out the
worker's 30 s idle sleep. Mirror::journalled now says whether it added a line,
and memoryd wakes the worker when it did. The Wake lock is a leaf, taken under
the index lock as before.

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

crates/memoryd/src/serve.rs

@@ -228,9 +228,12 @@ impl Memoryd {
 
     /// With `[honcho]`: decide journalled edit `id` (the latest when `None`) into the ledger. Called
     /// under the index lock, so edits are decided in the journal's order (M5c spec, section 4).
+    /// What it decided is sent at once: the worker is woken.
     fn mirror(&self, id: Option<&str>) {
-        if let Some(mirror) = &self.mirror {
-            mirror.journalled(&self.store, id, Timestamp::now(), &*self.log);
+        if let Some(mirror) = &self.mirror
+            && mirror.journalled(&self.store, id, Timestamp::now(), &*self.log)
+        {
+            self.wake.notify();
         }
     }