triangle-close: bulk lateral linking for clustering coefficient

New command: `poc-memory triangle-close [MIN_DEG] [SIM] [MAX_PER_HUB]`

For each node above min_degree, finds pairs of its neighbors that
aren't directly connected and have text similarity above threshold.
Links them. This turns hub-spoke patterns into triangles, directly
improving clustering coefficient and schema fit.

First run results (default params: deg≥5, sim≥0.3, max 10/hub):
- 636 hubs processed, 5046 lateral links added
- cc: 0.14 → 0.46  (target: high)
- fit: 0.09 → 0.32  (target ≥0.2)
- σ:  56.9 → 84.4  (small-world coefficient improved)

Also fixes separator agent prompt: truncate interference pairs to
batch count (was including all 1114 pairs = 1.3M chars).

src/main.rs

@@ -87,6 +87,7 @@ fn main() {
         "link-impact"           => cmd_link_impact(&args[2..]),
         "consolidate-session"   => cmd_consolidate_session(),
         "consolidate-full"      => cmd_consolidate_full(),
+        "triangle-close"        => cmd_triangle_close(&args[2..]),
         "daily-check"           => cmd_daily_check(),
         "apply-agent"           => cmd_apply_agent(&args[2..]),
         "digest"                => cmd_digest(&args[2..]),
@@ -149,6 +150,8 @@ Commands:
   link-impact SOURCE TARGET Simulate adding an edge, report topology impact
   consolidate-session       Analyze metrics, plan agent allocation
   consolidate-full          Autonomous: plan → agents → apply → digests → links
+  triangle-close [DEG] [SIM] [MAX]
+                            Close triangles: link similar neighbors of hubs
   daily-check               Brief metrics check (for cron/notifications)
   apply-agent [--all]       Import pending agent results into the graph
   digest daily [DATE]       Generate daily episodic digest (default: today)
@@ -437,6 +440,26 @@ fn cmd_consolidate_full() -> Result<(), String> {
     digest::consolidate_full(&mut store)
 }
 
+fn cmd_triangle_close(args: &[String]) -> Result<(), String> {
+    let min_degree: usize = args.first()
+        .and_then(|s| s.parse().ok())
+        .unwrap_or(5);
+    let sim_threshold: f32 = args.get(1)
+        .and_then(|s| s.parse().ok())
+        .unwrap_or(0.3);
+    let max_per_hub: usize = args.get(2)
+        .and_then(|s| s.parse().ok())
+        .unwrap_or(10);
+
+    println!("Triangle closure: min_degree={}, sim_threshold={}, max_per_hub={}",
+        min_degree, sim_threshold, max_per_hub);
+
+    let mut store = capnp_store::Store::load()?;
+    let (hubs, added) = neuro::triangle_close(&mut store, min_degree, sim_threshold, max_per_hub);
+    println!("\nProcessed {} hubs, added {} lateral links", hubs, added);
+    Ok(())
+}
+
 fn cmd_daily_check() -> Result<(), String> {
     let store = capnp_store::Store::load()?;
     let report = neuro::daily_check(&store);