Similar versions: surface-overlap metric + endpoint + UI panel

Ranks catalogued engine versions by how much of their CMC_* surface they share,
which (unlike a binary fuzzy hash) stays meaningful across compilers — the golden
pair PIKLIB8/MSVC6 vs bloomoodll/MSVC8 scores 85%.

- similarity.py: jaccard, surface_similarity (per-axis + pooled overall),
  fuzzy_similarity (ssdeep via ppdeep, secondary signal)
- service.similar_snapshots + GET /snapshots/{id}/similar?min=N (SimilarHit)
- UI: "Podobne wersje" panel in the snapshot browser (overlap bar + ⇄ diff)
- tests: 6 new (jaccard, identical/disjoint, golden pair 0<x<100, fuzzy,
  endpoint + min filter) -> 28/28

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ams/api/static/app.js

@@ -273,6 +273,9 @@ async function browse(id) {
   ];
   out.innerHTML = "";
   out.append(el("div", { class: "diff-head" }, "Przegląd: ", el("b", {}, `${snap.binary_name} [${snap.engine}/${snap.compiler}]`)));
+  const simBox = el("div", { class: "similar" });
+  out.append(simBox);
+  loadSimilar(id, simBox);
   const filter = el("input", { class: "owner browse-filter", placeholder: "filtruj…", oninput: () => render() });
   const tabbar = el("div", {});
   const list = el("div", {});
@@ -292,6 +295,27 @@ async function browse(id) {
   render();
 }
 
+async function loadSimilar(targetId, box) {
+  let hits;
+  try { hits = await jget("/snapshots/" + targetId + "/similar"); }
+  catch { return; }  // endpoint absent / single-snapshot catalog — just show nothing
+  if (!hits.length) return;
+  box.append(el("div", { class: "similar-title" }, "Podobne wersje (overlap powierzchni)"));
+  for (const h of hits.slice(0, 6)) {
+    const s = h.snapshot;
+    const bar = el("span", { class: "simbar" },
+      el("span", { class: "simfill", style: "width:" + h.overall + "%" }));
+    box.append(el("div", { class: "simrow" },
+      el("span", { class: "simscore" }, h.overall + "%"),
+      bar,
+      el("span", { class: "simname", title: "przejrzyj", onclick: () => browse(s.id) },
+        `${s.binary_name} [${s.engine || "?"}]`),
+      h.fuzzy != null ? el("span", { class: "simfuzzy", title: "ssdeep binarki" }, "fuzzy " + h.fuzzy) : null,
+      el("span", { class: "simdiff", title: "porównaj tę wersję z aktualną",
+        onclick: () => { state.a = targetId; state.b = s.id; refreshSelection(); compare(); } }, "⇄ diff")));
+  }
+}
+
 // --- boot -------------------------------------------------------------------------------------
 $("compare").addEventListener("click", compare);
 $("owner").addEventListener("keydown", (e) => { if (e.key === "Enter") compare(); });