feat(palette): unify quick open into command palette with multi-source search

Merge file picker into command palette. Single Cmd+P entry searches
files, sessions, settings pages and commands; groups re-order by best
fuzzy score per source. Sessions show branch labels; git status is
lazily fetched for all session directories on open.

Drop QuickOpenDialog and Cmd+K shortcut.

packages/ui/src/lib/search/fuzzySearch.ts

@@ -107,6 +107,67 @@ export function filterByFuzzyQuery<T>(
   return matching;
 }
 
+/**
+ * Score-sorted fuzzy ranking. Strict (low threshold), prioritizes substring
+ * matches (especially prefix matches), and returns the top N.
+ *
+ * Use this for command-palette-style result ranking where order matters more
+ * than recall.
+ */
+export function scoreByFuzzyQuery<T>(
+  items: T[],
+  query: string,
+  getText: (item: T) => string,
+  options?: { limit?: number; threshold?: number; noFuzzy?: boolean },
+): { item: T; score: number }[] {
+  if (!query) return items.map((item) => ({ item, score: 0 }));
+  const limit = options?.limit ?? items.length;
+  const threshold = options?.threshold ?? 0.3;
+  const noFuzzy = options?.noFuzzy ?? false;
+  const queryLower = query.toLowerCase();
+
+  const scored: { item: T; score: number }[] = [];
+  const fuzzyCandidates: { item: T; text: string }[] = [];
+
+  for (const item of items) {
+    const text = getText(item);
+    if (!text) continue;
+    const lower = text.toLowerCase();
+    const idx = lower.indexOf(queryLower);
+    if (idx === 0) {
+      scored.push({ item, score: -1 });
+      continue;
+    }
+    if (idx > 0) {
+      scored.push({ item, score: idx / 1000 });
+      continue;
+    }
+    if (!noFuzzy) fuzzyCandidates.push({ item, text });
+  }
+
+  if (fuzzyCandidates.length > 0) {
+    const fuse = new Fuse(
+      fuzzyCandidates.map((c) => c.text),
+      { threshold, ignoreLocation: true, distance: 100, includeScore: true, minMatchCharLength: 2 },
+    );
+    for (const result of fuse.search(query)) {
+      scored.push({ item: fuzzyCandidates[result.refIndex].item, score: result.score ?? 1 });
+    }
+  }
+
+  scored.sort((a, b) => a.score - b.score);
+  return scored.slice(0, limit);
+}
+
+export function rankByFuzzyQuery<T>(
+  items: T[],
+  query: string,
+  getText: (item: T) => string,
+  options?: { limit?: number; threshold?: number; noFuzzy?: boolean },
+): T[] {
+  return scoreByFuzzyQuery(items, query, getText, options).map((x) => x.item);
+}
+
 export function partitionByFuzzyQuery<T>(
   items: T[],
   query: string,