Fixed
- pubmed_fetch_fulltext now resolves PMID→PMCID via the NCBI PMC ID
  Converter API (NcbiService.idConvert) instead of eLink. eLink's
  exLinkSrv2 backend had a sustained outage on 2026-04-20 that broke
  every fulltext call; the ID Converter runs on a different backend
  and stayed up throughout. Equivalent coverage, batch-friendly, and
  drops ~30 lines of ELink XML type shims. Closes #16.

Changed
- Dependency: @cyanheads/mcp-ts-core 0.3.7 → 0.4.1. Brings OTel prompt
  telemetry (0.4.1), Vitest 4 projects helpers (0.4.0), and the
  duplicate "Error:" prefix fix (0.3.8). No handler-facing API changes.
- Skill sync: skills/api-utils refreshed from the framework — adds
  withRetry options table and partial-success batch metric docs.