fix: support has/missing conditions on config headers and fix glob exclude patterns in routing

[erayack]

Summary

Fixes config headers() matcher parity with redirects/rewrites by adding has/missing condition evaluation, and hardens behavior to fail closed when conditional header rules are evaluated without request context.

What changed

• Added has/missing support to config header matching in shared matcher and dev server path.
• Passed request context into header matching in prod server.
• Extended NextHeader typing to include has and missing.
• Added/updated tests:
  • Enabled E2E coverage for config headers with cookie has/missing conditions.
  • Added unit tests for matchHeaders, including no-context fail-closed behavior.
  • Fixed a flaky pages-router E2E (next/dynamic) by replacing ambiguous text locator with an exact heading-role locator.

Why

Previously, headers() rules only matched source and ignored request-context conditions, causing behavior mismatch with redirects/rewrites and Next.js compatibility gaps.

Validation

pnpm test tests/shims.test.ts -t "matchHeaders"
pnpm exec playwright test tests/e2e/app-router/config-redirect.spec.ts --grep "config headers with has/missing conditions"
CI=true PLAYWRIGHT_PROJECT=pages-router pnpm exec playwright test tests/e2e/pages-router/head-and-dynamic.spec.ts

[southpolesteve]

Hey @erayack, thanks for this PR! The core has/missing fix for config headers was already merged in #48, so there's overlap there. But your PR had several other valuable improvements that we've extracted into separate PRs (with you as commit author):

• fix: use exact heading locator in next/dynamic E2E to fix flaky test #209 — Flaky E2E test fix: exact heading locator for next/dynamic test
• fix: use function form of glob exclude for Node < 22.14 compat #212 — Glob exclude compat: the string array form of exclude on node:fs/promises glob requires Node >= 22.14, but our engines field allows >= 22. Your approach of filtering differently was spot-on.
• fix: make RequestContext required on matchHeaders/matchRedirect/matchRewrite #213 — Make RequestContext required on matchHeaders/matchRedirect/matchRewrite. Your PR used a fail-closed approach for missing context. We took that further and made ctx required entirely, since Next.js never evaluates these without a request. This also caught a missing reqCtx in deploy.ts.

Going to close this PR since the individual pieces are covered, but really appreciate the contribution. Each of those PRs credits you as the commit author.

[erayack]

Sounds great! Thanks for splitting these up and for the credit on the separate PRs. Glad I could help! @southpolesteve