stop filtering journal/digest nodes from knowledge and search

Journal and digest nodes are episodic memory — they should participate
in the graph on the same terms as everything else. Remove all
journal#/daily-/weekly-/monthly- skip filters from knowledge
extraction, connector pairs, challenger, semantic keys, and link
candidate selection. Use node_type field instead of key name matching
for episodic/semantic classification.

Operational nodes (MEMORY, where-am-i, work-queue, work-state) are
still filtered — they're system state, not memory.

Co-Authored-By: ProofOfConcept <poc@bcachefs.org>

src/llm.rs

@@ -133,17 +133,11 @@ pub(crate) fn parse_json_response(response: &str) -> Result<serde_json::Value, S
     Err(format!("no valid JSON in response: {preview}..."))
 }
 
-/// Get semantic keys (non-journal, non-system) for prompt context.
+/// Get non-operational keys for prompt context.
 pub(crate) fn semantic_keys(store: &Store) -> Vec<String> {
+    let skip = ["MEMORY", "where-am-i", "work-queue", "work-state"];
     let mut keys: Vec<String> = store.nodes.keys()
-        .filter(|k| {
-            !k.starts_with("journal#")
-            && *k != "journal"
-            && *k != "MEMORY"
-            && *k != "where-am-i"
-            && *k != "work-queue"
-            && *k != "work-state"
-        })
+        .filter(|k| !skip.contains(&k.as_str()))
         .cloned()
         .collect();
     keys.sort();