refactor(structure): reorganize codebase into domain-focused modules

src/timeline/mod.rs

@@ -0,0 +1,11 @@
+mod types;
+
+pub mod collect;
+pub mod expand;
+pub mod seed;
+
+pub use types::{
+    EntityRef, ExpandedEntityRef, MatchedDiscussion, THREAD_MAX_NOTES, THREAD_NOTE_MAX_CHARS,
+    ThreadNote, TimelineEvent, TimelineEventType, TimelineResult, UnresolvedRef,
+    resolve_entity_by_iid, resolve_entity_ref,
+};