feat(stdlib): implement WHATWG Fetch Request/Response and URLPattern with regex runtime hardening

[phamtanminhtien]

Overview

This PR completes WHATWG Fetch (Request, Response, fetch) compliance in node:http, implements WHATWG / WinterCG URLPattern in node:urlpattern and node:url, and hardens POSIX regex runtime handling for non-capturing groups and JS capture indices.

Key Changes

1. WHATWG Fetch (Request & Response)

• Body Readers: Added full body decoders on both Request and Response:
  • .text(): Promise<string>
  • .json(): Promise<unknown>
  • .arrayBuffer(): Promise<ArrayBuffer>
  • .blob(): Promise<Blob>
  • .bytes(): Promise<Uint8Array>
  • .formData(): Promise<FormData> (handles multipart/form-data with boundary parser and application/x-www-form-urlencoded)
• Body Serialization:
  • Automatically serializes FormData bodies to multipart/form-data with randomly generated boundaries.
  • Automatically normalizes BodyInit inputs (string, Blob, ArrayBuffer, Uint8Array, FormData, URLSearchParams).
• Static Constructors:
  • Response.json(data, init)
  • Response.error()
  • Response.redirect(url, status)
• Cloning & Immutability:
  • Request.clone() and Response.clone().
  • WHATWG fetch() integrated with Request & Response contracts.

2. WHATWG / WinterCG URLPattern

• Fully implemented URLPattern in internal/typescriptgo/stdlib/urlpattern.ts per WHATWG URLPattern specification.
• Supports matching across all 8 URL components: protocol, username, password, hostname, port, pathname, search, and hash.
• Supports parameter patterns (:param), wildcards (*), optional tokens (:param?), and regex constraints (:id(\\d+)).
• Supports base URL resolution, test(), and exec() returning structured URLPatternResult.
• Exported in node:url, node:urlpattern, and registered as an automatic web global.

3. POSIX RegExp Runtime Hardening

• Added support for non-capturing groups (?:...) in internal/runtime/native/regex/runtime.c.
• Corrected regex group mapping so JS result arrays contain exactly 1 + js_group_count elements, skipping internal non-capturing groups.
• Properly sets undefined sentinel for unmatched optional groups (e.g. a(b)?c on "ac").

4. Corpus Tests & Documentation

• Updated internal/compiler/testdata/corpus/api/request.ts covering all body readers, methods, and headers.
• Updated internal/compiler/testdata/corpus/api/response.ts covering status codes, body decoders, static constructors, and clones.
• Added internal/compiler/testdata/corpus/api/urlpattern.ts verifying path matching, named parameters, wildcards, and URL component extraction.
• Updated docs/typescript-parity-report.md maintaining 430/430 (100.0%) parity.

Verification

• go test -count=1 ./... (All package tests passed, including corpus tests)
• go test -count=1 ./internal/typescriptgo/... (Passed)
• go run ./cmd/parity (430/430 100.0% passed)
• go build ./cmd/scriptgo (Passed)