fix(quick-1): fix 6 TS generator bugs for enum/repeated query params and more

Bug #1: Client enum query params now compare against UNSPECIFIED variant
  instead of empty string (e.g., !== "REGION_UNSPECIFIED")
Bug #2: Server enum query params now cast to enum type with UNSPECIFIED
  default (e.g., (params.get("region") ?? "REGION_UNSPECIFIED") as Region)
Bug #3: Server repeated string query params now use params.getAll()
  instead of params.get()
Bug #4: Client repeated string query params now use forEach+append
  for multi-value URL params
Bug #5: Server no longer emits duplicate const url for routes with
  both path params and query params
Bug #6: Client prefixes unused req with _ for empty request messages

- Update all affected golden files (query_params + http_verbs_comprehensive)
- Update httpgen, clientgen, openapiv3 golden files for new proto RPCs
- Lint auto-fix: fmt.Fprintf instead of WriteString(Sprintf)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: SebastienMelki