journal_tail: return typed Vec<JournalEntry>, remove Store::load from agent

- journal_tail returns Vec<JournalEntry> with key, content, created_at
- load_startup_journal uses typed API, no more direct Store access
- CLI does formatting, hippocampus returns data

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

src/hippocampus/mod.rs

@@ -257,31 +257,46 @@ pub fn memory_query(store: &Store, _provenance: &str, query_str: &str, format: O
 
 // ── Journal tools ──────────────────────────────────────────────
 
-pub fn journal_tail(store: &Store, _provenance: &str, count: Option<u64>, level: Option<u64>, format: Option<&str>, after: Option<&str>) -> Result<String> {
-    let count = count.unwrap_or(1);
-    let level = level.unwrap_or(0);
-    let format = format.unwrap_or("full");
+/// A journal entry with key, content, and timestamp.
+#[derive(Clone, Debug, serde::Serialize, serde::Deserialize)]
+pub struct JournalEntry {
+    pub key: String,
+    pub content: String,
+    pub created_at: i64,
+}
 
-    let type_name = match level {
-        0 => "episodic",
-        1 => "daily",
-        2 => "weekly",
-        3 => "monthly",
-        _ => return Err(anyhow::anyhow!("invalid level: {} (0=journal, 1=daily, 2=weekly, 3=monthly)", level)),
+/// Get journal entries, sorted by timestamp (newest first).
+/// level: 0=session, 1=daily, 2=weekly, 3=monthly
+/// after: only entries after this date (YYYY-MM-DD)
+pub fn journal_tail(store: &Store, _provenance: &str, count: Option<u64>, level: Option<u64>, after: Option<&str>) -> Result<Vec<JournalEntry>> {
+    let count = count.unwrap_or(10) as usize;
+    let level = level.unwrap_or(0);
+    let node_type = match level {
+        0 => crate::store::NodeType::EpisodicSession,
+        1 => crate::store::NodeType::EpisodicDaily,
+        2 => crate::store::NodeType::EpisodicWeekly,
+        3 => crate::store::NodeType::EpisodicMonthly,
+        _ => return Err(anyhow::anyhow!("invalid level: {}", level)),
     };
 
-    let mut q = std::format!("all | type:{} | sort:timestamp", type_name);
-    if let Some(date) = after {
-        // Convert date to age in seconds
-        if let Ok(nd) = chrono::NaiveDate::parse_from_str(date, "%Y-%m-%d") {
-            let ts = nd.and_hms_opt(0, 0, 0).unwrap().and_utc().timestamp();
-            let age = chrono::Utc::now().timestamp() - ts;
-            q.push_str(&std::format!(" | age:<{}", age));
-        }
-    }
-    q.push_str(&std::format!(" | limit:{}", count));
+    let after_ts = after.and_then(|date| {
+        chrono::NaiveDate::parse_from_str(date, "%Y-%m-%d").ok()
+            .and_then(|nd| nd.and_hms_opt(0, 0, 0))
+            .map(|dt| dt.and_utc().timestamp())
+    });
 
-    memory_query(store, _provenance, &q, Some(format))
+    let mut entries: Vec<_> = store.nodes.values()
+        .filter(|n| n.node_type == node_type)
+        .filter(|n| after_ts.map(|ts| n.created_at >= ts).unwrap_or(true))
+        .map(|n| JournalEntry {
+            key: n.key.clone(),
+            content: n.content.clone(),
+            created_at: n.created_at,
+        })
+        .collect();
+    entries.sort_by_key(|e| std::cmp::Reverse(e.created_at));
+    entries.truncate(count);
+    Ok(entries)
 }
 
 fn level_to_node_type(level: i64) -> crate::store::NodeType {