fix(fetch): preserve Request __sapiom metadata - #691

Summary

Fixes #690

@sapiom/fetch documents per-request overrides by attaching __sapiom metadata directly to a Request, including { enabled: false } to bypass Sapiom for one request.

However, createFetch() cloned the input with new Request(input, init) before reading metadata. Native Request cloning does not preserve custom properties, so Request.__sapiom was lost.

This PR preserves the metadata before cloning and reattaches it to cloned requests so per-request overrides keep working.

Changes

• Read __sapiom metadata from the original Request before cloning.
• Reattach metadata to the cloned request.
• Preserve metadata across later internal request clones.
• Add a regression test for Request.__sapiom = { enabled: false }.

How to Test

corepack pnpm --filter @sapiom/fetch test
corepack pnpm --filter @sapiom/fetch lint
corepack pnpm --filter @sapiom/fetch typecheck
corepack pnpm --filter @sapiom/fetch build
git diff --check

Checklist

• Tests pass — new regression test covers Request.__sapiom = { enabled: false }
• Lint, typecheck, and build clean
• Follows Conventional Commits
• Changes scoped to this fix only

Risk & Impact

Low. The fix only affects how __sapiom metadata survives internal Request cloning — it reads and reattaches the metadata rather than changing any clone or fetch behavior. Requests without __sapiom metadata are unaffected.

Type: 🐛 Bug fix
Fixes: #690