memory: append creates the directory it writes into

write has always called create_dir_all; append never did, so an append under
a directory that did not exist yet failed ENOENT. Every subconscious surfacing
to system/metacognition/subconscious.md was lost this way — three WARNs at
00:01:40 on 2026-08-17, and the directory had never existed in the repo's
history.

src/core/memory/mod.rs

@@ -492,6 +492,17 @@ impl MemoryRepo {
     pub async fn append(&self, label: &str, content: &str) -> Result<()> {
         let path = self.resolve_path(label);
 
+        // `write` has always created parent directories; `append` never did,
+        // so appending to a file under a directory that does not exist yet
+        // failed ENOENT. Measured 2026-08-17: every inner-voice surfacing to
+        // `system/metacognition/subconscious.md` was lost this way, because
+        // nothing ever created `system/metacognition/`.
+        if let Some(parent) = path.parent() {
+            tokio::fs::create_dir_all(parent)
+                .await
+                .context("creating parent directories")?;
+        }
+
         // Frontmatter never belongs mid-file; merge it instead of nesting.
         let (supplied, content) = split_supplied_frontmatter(content);
 
@@ -1869,11 +1880,29 @@ mod tests {
     }
 
     #[tokio::test]
-    async fn test_memory_repo_list() {
+    async fn append_creates_missing_parent_directories() {
+        // The inner-voice path: nothing ever created `system/metacognition/`,
+        // so every append to it failed ENOENT and the surfacing was lost.
         let dir = TempDir::new().unwrap();
         let repo = MemoryRepo::new("test-agent", dir.path());
         repo.init().await.unwrap();
 
+        repo.append("system/metacognition/subconscious.md", "a thought")
+            .await
+            .expect("append must create the parent directory");
+
+        let written = repo
+            .read("system/metacognition/subconscious.md")
+            .await
+            .unwrap();
+        assert!(written.body.contains("a thought"));
+    }
+
+    #[tokio::test]
+    async fn test_memory_repo_list() {        let dir = TempDir::new().unwrap();
+        let repo = MemoryRepo::new("test-agent", dir.path());
+        repo.init().await.unwrap();
+
         let entries = repo.list(None).await.unwrap();
         assert!(entries.iter().any(|e| e == "system/"));
     }