refactor: extract Store methods, clean up shell-outs

- Add Store::upsert() — generic create-or-update, used by cmd_write
- Add Store::insert_node() — for pre-constructed nodes (journal entries)
- Add Store::delete_node() — soft-delete with version bump
- Simplify cmd_write (20 → 8 lines), cmd_node_delete (16 → 7 lines),
  cmd_journal_write (removes manual append/insert/save boilerplate)
- Replace generate_cookie shell-out to head/urandom with direct
  /dev/urandom read + const alphabet table

main.rs: 1137 → 1109 lines.

src/bin/memory-search.rs

@@ -150,19 +150,12 @@ fn load_or_create_cookie(dir: &Path, session_id: &str) -> String {
 }
 
 fn generate_cookie() -> String {
-    let out = Command::new("head")
-        .args(["-c", "12", "/dev/urandom"])
-        .output()
+    const ALPHA: &[u8] = b"0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
+    let mut buf = [0u8; 16];
+    fs::File::open("/dev/urandom")
+        .and_then(|mut f| io::Read::read_exact(&mut f, &mut buf))
         .expect("failed to read urandom");
-    out.stdout.iter()
-        .map(|b| {
-            let idx = (*b as usize) % 62;
-            if idx < 10 { (b'0' + idx as u8) as char }
-            else if idx < 36 { (b'a' + (idx - 10) as u8) as char }
-            else { (b'A' + (idx - 36) as u8) as char }
-        })
-        .take(16)
-        .collect()
+    buf.iter().map(|b| ALPHA[(*b as usize) % ALPHA.len()] as char).collect()
 }
 
 fn load_seen(dir: &Path, session_id: &str) -> HashSet<String> {

src/capnp_store.rs

@@ -491,6 +491,48 @@ impl Store {
         Ok(())
     }
 
+    /// Upsert a node: update if exists (and content changed), create if not.
+    /// Returns: "created", "updated", or "unchanged".
+    pub fn upsert(&mut self, key: &str, content: &str) -> Result<&'static str, String> {
+        if let Some(existing) = self.nodes.get(key) {
+            if existing.content == content {
+                return Ok("unchanged");
+            }
+            let mut node = existing.clone();
+            node.content = content.to_string();
+            node.version += 1;
+            self.append_nodes(std::slice::from_ref(&node))?;
+            self.nodes.insert(key.to_string(), node);
+            Ok("updated")
+        } else {
+            let node = Store::new_node(key, content);
+            self.append_nodes(std::slice::from_ref(&node))?;
+            self.uuid_to_key.insert(node.uuid, node.key.clone());
+            self.nodes.insert(key.to_string(), node);
+            Ok("created")
+        }
+    }
+
+    /// Soft-delete a node (appends deleted version, removes from cache).
+    pub fn delete_node(&mut self, key: &str) -> Result<(), String> {
+        let node = self.nodes.get(key)
+            .ok_or_else(|| format!("No node '{}'", key))?;
+        let mut deleted = node.clone();
+        deleted.deleted = true;
+        deleted.version += 1;
+        self.append_nodes(std::slice::from_ref(&deleted))?;
+        self.nodes.remove(key);
+        Ok(())
+    }
+
+    /// Insert a fully constructed node (for journal entries, imports, etc.)
+    pub fn insert_node(&mut self, node: Node) -> Result<(), String> {
+        self.append_nodes(std::slice::from_ref(&node))?;
+        self.uuid_to_key.insert(node.uuid, node.key.clone());
+        self.nodes.insert(node.key.clone(), node);
+        Ok(())
+    }
+
     /// Create a new node with defaults
     pub fn new_node(key: &str, content: &str) -> Node {
         Node {

src/main.rs

@@ -793,24 +793,10 @@ fn cmd_node_delete(args: &[String]) -> Result<(), String> {
     let key = args.join(" ");
     let mut store = capnp_store::Store::load()?;
     let resolved = store.resolve_key(&key)?;
-
-    let updated = if let Some(node) = store.nodes.get_mut(&resolved) {
-        node.deleted = true;
-        node.version += 1;
-        Some(node.clone())
-    } else {
-        None
-    };
-
-    if let Some(node) = updated {
-        store.append_nodes(&[node])?;
-        store.nodes.remove(&resolved);
+    store.delete_node(&resolved)?;
     store.save()?;
     println!("Deleted '{}'", resolved);
     Ok(())
-    } else {
-        Err(format!("No node '{}'", resolved))
-    }
 }
 
 fn cmd_load_context() -> Result<(), String> {
@@ -923,27 +909,15 @@ fn cmd_write(args: &[String]) -> Result<(), String> {
     }
 
     let mut store = capnp_store::Store::load()?;
-
-    if let Some(existing) = store.nodes.get(&key) {
-        if existing.content == content {
-            println!("No change: '{}'", key);
-            return Ok(());
+    let result = store.upsert(&key, &content)?;
+    match result {
+        "unchanged" => println!("No change: '{}'", key),
+        "updated" => println!("Updated '{}' (v{})", key, store.nodes[&key].version),
+        _ => println!("Created '{}'", key),
     }
-        let mut node = existing.clone();
-        node.content = content;
-        node.version += 1;
-        store.append_nodes(std::slice::from_ref(&node))?;
-        store.nodes.insert(key.clone(), node);
-        println!("Updated '{}' (v{})", key, store.nodes[&key].version);
-    } else {
-        let node = capnp_store::Store::new_node(&key, &content);
-        store.append_nodes(std::slice::from_ref(&node))?;
-        store.uuid_to_key.insert(node.uuid, node.key.clone());
-        store.nodes.insert(key.clone(), node);
-        println!("Created '{}'", key);
-    }
-
+    if result != "unchanged" {
         store.save()?;
+    }
     Ok(())
 }
 
@@ -1055,13 +1029,11 @@ fn cmd_journal_write(args: &[String]) -> Result<(), String> {
     let mut node = capnp_store::Store::new_node(&key, &content);
     node.node_type = capnp_store::NodeType::EpisodicSession;
     node.provenance = capnp_store::Provenance::Journal;
-    if let Some(ref src) = source_ref {
-        node.source_ref = src.clone();
+    if let Some(src) = source_ref {
+        node.source_ref = src;
     }
 
-    store.append_nodes(&[node.clone()])?;
-    store.uuid_to_key.insert(node.uuid, node.key.clone());
-    store.nodes.insert(key.clone(), node);
+    store.insert_node(node)?;
     store.save()?;
 
     let word_count = text.split_whitespace().count();