fix: Pages API body parser for invalid JSON and repeated form keys

[JaredStowell]

Bring Pages API body parsing in line with Next.js for JSON and urlencoded requests.

Changes

• return 400 Invalid JSON for malformed application/json requests instead of passing raw strings to handlers
• preserve duplicate application/x-www-form-urlencoded keys as arrays via querystring.decode()
• treat empty JSON bodies as {} to match Next.js behavior
• recognize application/ld+json as JSON
• avoid logging/reporting invalid JSON as a server error
• preserve response statusText through the Pages production server path
• add dev and production regression coverage for all of the above

Testing

• pnpm test tests/api-handler.test.ts tests/pages-router.test.ts tests/entry-templates.test.ts -u
• pnpm test tests/features.test.ts -t "production server compression"
• pnpm run fmt
• pnpm run typecheck

[pkg-pr-new]

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commit: 78ce4e5

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Drop stale status text when rewrite overrides status

When middlewareRewriteStatus overrides the downstream response status, this call still forwards response.statusText, so the reason phrase can describe a different status code than the one actually sent (for example, a middleware rewrite to 403 combined with an API response that set statusText to Invalid JSON yields 403 Invalid JSON). This mismatch was introduced by propagating statusText and affects any rewritten API/page response with a custom status text; only preserve response.statusText when the final status code is unchanged.

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