remove hardcoded skip lists, prune orphan edges in fsck

All nodes in the store are memory — none should be excluded from
knowledge extraction, search, or graph algorithms by name. Removed
the MEMORY/where-am-i/work-queue/work-state skip lists entirely.
Deleted where-am-i and work-queue nodes from the store (ephemeral
scratchpads that don't belong). Added orphan edge pruning to fsck
so broken links get cleaned up automatically.

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

src/llm.rs

@@ -133,11 +133,9 @@ pub(crate) fn parse_json_response(response: &str) -> Result<serde_json::Value, S
     Err(format!("no valid JSON in response: {preview}..."))
 }
 
-/// Get non-operational keys for prompt context.
+/// Get all 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| !skip.contains(&k.as_str()))
         .cloned()
         .collect();
     keys.sort();