fix(middleware): clear request timeout on close and propagate abort signal downstream (closes #910)

[mopxam-art]

Overview

Closes #910 by ensuring that the pending request timer in requestTimeout middleware is cleared immediately when a client aborts/disconnects early (res.once("close")), preventing retained timer accumulation and subsequent write errors against dead responses. Additionally attaches an AbortController signal to req.signal, propagating cancellation to downstream handlers when a timeout expires or when the client disconnects before the response completes.

Changes

• src/middleware/requestTimeout.ts:
  • Added res.once("close") handler alongside finish to clear the pending timer upon early client disconnect.
  • Instantiated AbortController and attached its signal to (req as RequestWithSignal).signal.
  • Aborted downstream signal on timeout (Request Timeout) and on premature client disconnect (Client disconnected).
  • Added bounds checking in getTimeoutMs to fall back cleanly to defaults (30000ms / 60000ms) on invalid or non-positive environment variables.
• src/__tests__/requestTimeout-5d-matrix.test.ts:
  • Added 114 tests across the 5D matrix verifying boundaries, timeout configuration, status code lifecycles, client disconnect timer leak prevention, idempotency, and concurrent request stress.

Verification

• All 114 tests pass green (npx jest src/__tests__/requestTimeout-5d-matrix.test.ts).
• TypeScript typecheck passes with 0 errors (npx tsc --noEmit).
• ESLint passes with 0 warnings/errors.
• Production build succeeds cleanly (npm run build).