migrate more files to use index-based node access

- learn.rs, daemon.rs, graph.rs, digest.rs, prompts.rs
- Convert store.nodes.get() → store.get_node()
- Convert store.nodes.contains_key() → store.contains_key()
- Convert store.nodes.values/iter() → all_keys + get_node

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

src/subconscious/digest.rs

@@ -112,17 +112,21 @@ fn parse_digest_node_links(key: &str, content: &str) -> Vec<DigestLink> {
 pub fn parse_all_digest_links(store: &Store) -> Vec<DigestLink> {
     let mut all_links = Vec::new();
 
-    let mut digest_keys: Vec<&String> = store.nodes.iter()
-        .filter(|(_, n)| matches!(n.node_type,
-            store::NodeType::EpisodicDaily
-            | store::NodeType::EpisodicWeekly
-            | store::NodeType::EpisodicMonthly))
-        .map(|(k, _)| k)
+    let all_keys = store.all_keys().unwrap_or_default();
+    let mut digest_keys: Vec<String> = all_keys.into_iter()
+        .filter(|k| {
+            store.get_node(k).ok().flatten()
+                .map(|n| matches!(n.node_type,
+                    store::NodeType::EpisodicDaily
+                    | store::NodeType::EpisodicWeekly
+                    | store::NodeType::EpisodicMonthly))
+                .unwrap_or(false)
+        })
         .collect();
     digest_keys.sort();
 
-    for key in digest_keys {
-        if let Some(node) = store.nodes.get(key) {
+    for key in &digest_keys {
+        if let Ok(Some(node)) = store.get_node(key) {
             all_links.extend(parse_digest_node_links(key, &node.content));
         }
     }
@@ -178,11 +182,11 @@ pub fn apply_digest_links(store: &mut Store, links: &[DigestLink]) -> (usize, us
         );
         if exists { skipped += 1; continue; }
 
-        let source_uuid = match store.nodes.get(&source) {
+        let source_uuid = match store.get_node(&source).ok().flatten() {
             Some(n) => n.uuid,
             None => { skipped += 1; continue; }
         };
-        let target_uuid = match store.nodes.get(&target) {
+        let target_uuid = match store.get_node(&target).ok().flatten() {
             Some(n) => n.uuid,
             None => { skipped += 1; continue; }
         };