store: remove dead code and move params to config

Remove:
- score_weight() - never called
- position field on Node - never read (was for export)
- Provenance enum - inline helper for capnp migration
- migrate_transcript_progress + CLI command
- init_from_markdown, import_file, ingest_units
- export command and export_to_markdown
- RetrievalEvent, GapRecord types
- classify_filename, new_transcript_segment

Move spreading activation params to Config:
- default_node_weight, edge_decay, max_hops, min_activation
- Remove Params struct and StoreView::params()

Simplify cmd_init to just seed identity via upsert().
Simplify cmd_import to use parse_units + upsert directly.

-576 lines

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

src/hippocampus/store/view.rs

@@ -21,9 +21,6 @@ pub trait StoreView {
 
     /// Node content by key.
     fn node_content(&self, key: &str) -> Option<&str>;
-
-    /// Search/graph parameters.
-    fn params(&self) -> Params;
 }
 
 impl StoreView for Store {
@@ -47,14 +44,11 @@ impl StoreView for Store {
     }
 
     fn node_weight(&self, key: &str) -> f64 {
-        self.nodes.get(key).map(|n| n.weight as f64).unwrap_or(self.params.default_weight)
+        let cfg = crate::config::get();
+        self.nodes.get(key).map(|n| n.weight as f64).unwrap_or(cfg.default_node_weight)
     }
 
     fn node_content(&self, key: &str) -> Option<&str> {
         self.nodes.get(key).map(|n| n.content.as_str())
     }
-
-    fn params(&self) -> Params {
-        self.params
-    }
 }