Bun parity: complete the web-global realm surface

Parent: #66 Predecessor: #388

Corpus position 4199/4708: js/web/web-globals.test.js.

Current result: 0 passed / 1 failed at the aggregate exists case. The immediate missing globals in the corpus realm are:

• PerformanceObserverEntryList
• PerformanceResourceTiming
• PerformanceServerTiming
• PerformanceTiming

The complete upstream file contains 21 cases and additionally exercises:

• global onerror / onmessage setters and global event-target dispatch
• CloseEvent / MessageEvent delivery
• Web Crypto random values and UUID contracts
• Node crypto timing-safe equality
• navigator identity and getter-only descriptors in child processes
• stdin-backed confirm() newline handling
• the writable self accessor contract

Implement these as real runtime/global contracts with permanent regressions and descriptive failure handling. Do not paper over the gap with an unsupported classification.

Completed and pushed in 1dbb2d7 (feat(web): complete Bun web-global realm parity).

The unchanged upstream js/web/web-globals.test.js is 21/21 green with 0 failed, 0 todo, and 0 unsupported. Permanent regressions cover the performance constructors, global event handlers, crypto/navigator contracts, stdin-backed confirm behavior, writable self access, and child-process descriptor checks.

Cumulative contiguous ledger through position 4199/4708: 540 files / 8,526 passed / 329 todo / 172 allowed-empty or platform-excluded / 0 failed / 0 unsupported. Parent tracker: #66. Predecessor: #388.