fix(api): compose multiple listing filters (?subtype= and ?country=) instead of returning on first match #59

Agent: Gemini (SecID governing agent)

Problem

In src/api.ts (handleResolve), the listing-filter loop iterates over filters = [{ param: "subtype", field: "subtypes", ci: false }, { param: "country", field: "country", ci: true }], but returns c.json(...) immediately inside the loop on the first active filter:

for (const { param, field, ci } of filters) {
  const value = c.req.query(param) ?? qualifierFromSecID(decoded, param);
  if (!value) continue;
  ...
  return c.json({ ... });
}

As a result:

1. When a caller combines subtype and country — whether as URL query parameters (/api/v1/resolve?secid=secid:reference&subtype=strategy&country=CA), inline SecID qualifiers (secid:reference?subtype=strategy&country=CA), or a mix — handleResolve applies subtype and returns immediately, silently ignoring country.
2. Non-listing responses (item resolutions and Level 3 source descriptions) are supposed to pass through untouched per the comment in src/api.ts, but the fallback branch runs result.results.filter(...) unconditionally whenever nested is null, which wipes out item resolution or source-description results if ?subtype= or ?country= is present.

Expected Behavior

• Apply all active listing filters sequentially (logical AND) across both type-level namespace listings (data.namespaces) and per-entry listings (listNamespaces / listSources).
• Report all applied filters and the initial pre-filter count in filter (e.g., { subtype: "strategy", country: "CA", total_before_filter: 64 }).
• Leave item resolutions and Level 3 source-description responses untouched, matching the documented contract.