feat(server): add institutional memory recall

- File-based memory under .boocode/memory/ (project/user/reference topics)
- Hierarchical 4-scope scan: global → home → project → session
- Keyword/tag relevance matching for query-based recall
- Injected as <boocode-memory> block in system prompt at assembly
- v1 recall-only (extract/dream deferred to v2)

apps/server/src/services/memory/recall.ts

@@ -0,0 +1,44 @@
+import type { MemoryEntry } from './entries.js';
+import { scanProjectMemory } from './scan.js';
+
+function extractKeywords(query: string): string[] {
+  return query
+    .toLowerCase()
+    .replace(/[^a-z0-9\s]/g, '')
+    .split(/\s+/)
+    .filter((w) => w.length > 2);
+}
+
+export function rankByRelevance(query: string, entries: MemoryEntry[]): MemoryEntry[] {
+  const keywords = extractKeywords(query);
+  if (keywords.length === 0) return entries.slice(0, 5);
+
+  const scored = entries.map((entry) => {
+    let score = 0;
+    const searchText = `${entry.title} ${entry.content} ${entry.tags.join(' ')}`.toLowerCase();
+    for (const kw of keywords) {
+      if (entry.title.toLowerCase().includes(kw)) score += 3;
+      if (entry.tags.some((t) => t.toLowerCase().includes(kw))) score += 2;
+      if (entry.content.toLowerCase().includes(kw)) score += 1;
+    }
+    return { entry, score };
+  });
+
+  return scored
+    .filter((s) => s.score > 0)
+    .sort((a, b) => b.score - a.score)
+    .slice(0, 10)
+    .map((s) => s.entry);
+}
+
+export async function loadMemoryForSession(
+  projectRoot: string,
+  _sessionId?: string,
+  query?: string,
+): Promise<string[]> {
+  const entries = await scanProjectMemory(projectRoot);
+  if (entries.length === 0) return [];
+
+  const relevant = query ? rankByRelevance(query, entries) : entries.slice(0, 5);
+  return relevant.map((e) => `[${e.topic}] ${e.title}: ${e.content}`);
+}