fix(typescript): classify connection failures

[NikolayS]

Summary

Fix REV rerun finding: TypeScript classified operation-time pool/network failures as generic PgqueSqlError, despite PgqueConnectionError documenting mid-operation drops and Go tagging non-PgError operation failures as connection errors.

• classify common Node/pg connection failures as PgqueConnectionError
• cover closed pool, terminated connection, and ECONNRESET with in-memory regression tests

Test

• cd clients/typescript && bun run check && bun run test (33 passed, 50 skipped locally without PGQUE_TEST_DSN)
• git diff --check

REV

REV rerun finding from #251: #251 (comment)

[NikolayS]

REV

Scope: TypeScript client parity/code review only. SOC2/compliance checklist skipped.

Finding addressed

REV rerun found that TypeScript still classified operation-time connection/pool failures as PgqueSqlError, while:

• PgqueConnectionError documents mid-operation connection drops.
• Go maps non-PgError operation failures as connection errors.

Review result

Clean for this focused follow-up.

What changed

• mapPgError() now returns PgqueConnectionError for common Node/pg connection failures:
  • ECONNRESET
  • ECONNREFUSED
  • EPIPE
  • ETIMEDOUT
  • ENOTFOUND
  • EAI_AGAIN
  • closed/terminated connection and ended pool message fragments
• Added in-memory regression tests for:
  • Connection terminated unexpectedly
  • Cannot use a pool after calling end on the pool
  • ECONNRESET

Gates

• cd clients/typescript && bun run check && bun run test → passed (33 passed, 50 skipped locally without PGQUE_TEST_DSN)
• git diff --check → clean

No remaining blocker found in this patch.