Delete similarity module, rewrite module, and all text-similarity code

Text cosine similarity was being used as a crutch for operations
the graph structure should handle: interference detection, orphan
linking, triangle closing, hub differentiation. These are all
graph-structural operations that the agents (linker, extractor)
handle with actual semantic understanding.

Removed: similarity.rs (stemming + cosine), rewrite.rs (orphan
linking, triangle closing, hub differentiation), detect_interference,
and all CLI commands and consolidation steps that used them.

-794 lines.

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

src/subconscious/digest.rs

@@ -7,7 +7,6 @@ use std::sync::Arc;
 // pipeline, parameterized by DigestLevel.
 
 use crate::store::{self, Store, new_relation};
-use crate::neuro;
 
 use chrono::{Datelike, Duration, Local, NaiveDate};
 use regex::Regex;
@@ -549,11 +548,6 @@ pub fn apply_digest_links(store: &mut Store, links: &[DigestLink]) -> (usize, us
             }
         };
 
-        // Refine target to best-matching section if available
-        let source_content = store.nodes.get(&source)
-            .map(|n| n.content.as_str()).unwrap_or("");
-        let target = neuro::refine_target(store, source_content, &target);
-
         if source == target { skipped += 1; continue; }
 
         // Check if link already exists