fix(api): listCaches reads __stats from prefix, not name

readBaseStats(client, key) constructs ${key}:__stats. listCaches was
passing marker.name; for caches whose discovery-marker name happens
to equal their prefix this is fine, but the protocol allows the two
to differ (e.g. an alias-style registration). Stats would then read
from the wrong key and report zeros even for an active cache.

Adds a regression test where ALIAS != PREFIX and asserts stats are
sourced from PREFIX.

Author: jamby77

apps/api/src/cache-proposals/__tests__/cache-readonly.service.spec.ts

@@ -132,6 +132,24 @@ describe('CacheReadonlyService', () => {
       expect(ac.status).toBe('stale');
     });
 
+    it('reads stats from prefix, not name, when they differ', async () => {
+      const { service, client } = await buildService();
+      const ALIAS = 'prod-llm';
+      const PREFIX = 'betterdb_scache_prod';
+      seedRegistry(client, {
+        [ALIAS]: { type: 'semantic_cache', prefix: PREFIX },
+      });
+      client.hashes[`${PREFIX}:__stats`] = { hits: '90', misses: '10', total: '100' };
+      client.hashes[`${ALIAS}:__stats`] = { hits: '0', misses: '0', total: '0' };
+
+      const result = await service.listCaches(CONNECTION_ID);
+      expect(result).toHaveLength(1);
+      expect(result[0].name).toBe(ALIAS);
+      expect(result[0].prefix).toBe(PREFIX);
+      expect(result[0].hit_rate).toBeCloseTo(0.9);
+      expect(result[0].total_ops).toBe(100);
+    });
+
     it('returns empty when registry is empty', async () => {
       const { service } = await buildService();
       const result = await service.listCaches(CONNECTION_ID);

apps/api/src/cache-proposals/cache-readonly.service.ts

@@ -83,7 +83,7 @@ export class CacheReadonlyService {
 
     const entries: CacheListEntry[] = [];
     for (const marker of markers) {
-      const stats = await this.readBaseStats(client, marker.name);
+      const stats = await this.readBaseStats(client, marker.prefix);
       const heartbeat = await client.get(heartbeatKeyFor(marker.name));
       const status: CacheListEntry['status'] = heartbeat === null ? 'stale' : 'live';
       entries.push({