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/hippocampus/cursor.rs

@@ -89,17 +89,13 @@ pub fn digest_parent(store: &Store, key: &str) -> Option<String> {
         if node.timestamp > 0 {
             dates.push(store::format_date(node.timestamp));
         }
-        // Extract date from key patterns like "journal#2026-03-03-..." or "journal#j-2026-03-13t..."
-        if let Some(rest) = key.strip_prefix("journal#j-").or_else(|| key.strip_prefix("journal#"))
-            && rest.len() >= 10 {
-                let candidate = &rest[..10];
-                if candidate.chars().nth(4) == Some('-') {
-                    let date = candidate.to_string();
-                    if !dates.contains(&date) {
-                        dates.push(date);
-                    }
-                }
+        // Extract date from created_at timestamp
+        if node.created_at > 0 {
+            let created_date = store::format_date(node.created_at);
+            if !dates.contains(&created_date) {
+                dates.push(created_date);
             }
+        }
         for date in &dates {
             for prefix in [&format!("daily-{}", date), &format!("digest#daily#{}", date)] {
                 for (k, n) in &store.nodes {

src/hippocampus/graph.rs

@@ -566,19 +566,14 @@ fn add_implicit_temporal_edges(
     use chrono::{Datelike, DateTime, NaiveDate};
 
     // Extract the covered date from a key name.
-    // Patterns: "daily-2026-03-06", "daily-2026-03-06-identity",
-    //           "weekly-2026-W09", "monthly-2026-02"
-    //           "journal#j-2026-03-13t...", "journal#2026-03-13-..."
+    // Patterns: "daily-2026-03-06", "daily-2026-03-06-identity"
     fn date_from_key(key: &str) -> Option<NaiveDate> {
-        // Try extracting YYYY-MM-DD after known prefixes
-        for prefix in ["daily-", "journal#j-", "journal#"] {
-            if let Some(rest) = key.strip_prefix(prefix)
-                && rest.len() >= 10
-                    && let Ok(d) = NaiveDate::parse_from_str(&rest[..10], "%Y-%m-%d") {
-                        return Some(d);
-                    }
+        let rest = key.strip_prefix("daily-")?;
+        if rest.len() >= 10 {
+            NaiveDate::parse_from_str(&rest[..10], "%Y-%m-%d").ok()
+        } else {
+            None
         }
-        None
     }
 
     fn week_from_key(key: &str) -> Option<(i32, u32)> {

src/hippocampus/store/mod.rs

@@ -48,7 +48,7 @@ use std::path::Path;
 use parse::classify_filename;
 
 /// Strip .md suffix from a key, handling both bare keys and section keys.
-/// "journal.md#j-2026" → "journal#j-2026", "identity.md" → "identity", "identity" → "identity"
+/// "identity.md" → "identity", "foo.md#section" → "foo#section", "identity" → "identity"
 pub fn strip_md_suffix(key: &str) -> String {
     if let Some((file, section)) = key.split_once('#') {
         let bare = file.strip_suffix(".md").unwrap_or(file);