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/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.save()?;
-        println!("Deleted '{}'", resolved);
-        Ok(())
-    } else {
-        Err(format!("No node '{}'", resolved))
-    }
+    store.delete_node(&resolved)?;
+    store.save()?;
+    println!("Deleted '{}'", resolved);
+    Ok(())
 }
 
 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 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);
+    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),
+    }
+    if result != "unchanged" {
+        store.save()?;
     }
-
-    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();