Bun parity: implement the URLPattern web API

Tracks Bun corpus frontier position 4197: js/web/urlpattern/urlpattern.test.ts.

Initial exact result: 0 pass, 1 fail, 0 unsupported. URLPattern is not defined. Scope is the complete upstream URLPattern constructor/test/exec matrix, component parsing and canonicalization, groups, base URLs, ignoreCase behavior, input validation, and durable diagnostics/permanent regressions.

Parent: #66 Predecessor: #387

Implemented and pushed in 0d46908 (feat(url): implement URLPattern web API).

Verification:

• Bun corpus js/web/urlpattern/urlpattern.test.ts: 408 passed, 0 failed, 0 todo, 0 unsupported
• Permanent Home URLPattern regression coverage: 4 passed
• URLPattern is installed in the runtime global surface, not only the corpus harness
• Runtime and test-harness polyfill sources are byte-identical
• zig build --cache-dir /private/tmp/home-zig-abi-cache: passed
• zig fmt --check: passed
• focused Pickier lint: passed
• JavaScript syntax check: passed

Parent tracker: #66. Predecessor: #387.