journal: remove all stringly-typed key patterns, use NodeType

- journal_new: key is slugified title (agent names things properly)
- journal_tail: sort by created_at (immutable), not timestamp (mutable)
- journal_update: find latest by created_at
- {{latest_journal}}: query by NodeType::EpisodicSession, not "journal" key
- poc-memory journal write: requires a name argument
- Removed all journal#j-{timestamp}-{slug} patterns from:
  - prompts.rs (rename candidates)
  - graph.rs (date extraction, organize skip list)
  - cursor.rs (date extraction)
  - store/mod.rs (doc comment)
- graph.rs organize: filter by NodeType::Semantic instead of key prefix
- cursor.rs: use created_at for date extraction instead of key parsing

Co-Authored-By: Kent Overstreet <kent.overstreet@linux.dev>

src/cli/graph.rs

@@ -480,12 +480,12 @@ pub fn cmd_organize(term: &str, threshold: f32, key_only: bool, create_anchor: b
     let term_lower = term.to_lowercase();
     let mut topic_nodes: Vec<(String, String)> = Vec::new(); // (key, content)
 
-    // Prefixes that indicate ephemeral/generated nodes to skip
-    let skip_prefixes = ["journal#", "daily-", "weekly-", "monthly-", "_",
-                         "deep-index#", "facts-", "irc-history#"];
+    let skip_prefixes = ["_", "deep-index#", "facts-", "irc-history#"];
 
     for (key, node) in &store.nodes {
         if node.deleted { continue; }
+        // Skip episodic/digest nodes — use NodeType, not key prefix
+        if node.node_type != crate::store::NodeType::Semantic { continue; }
         let key_matches = key.to_lowercase().contains(&term_lower);
         let content_matches = !key_only && node.content.to_lowercase().contains(&term_lower);
         if !key_matches && !content_matches { continue; }