Port Bun Worker postMessage transfer overloads

Tracks Bun corpus position 4231 (js/web/workers/worker-postmessage-transfer.test.ts).

Completed in bab20ca:

• Resolve string and URL-form Blob object URLs as Worker modules through the shared Blob module stack.
• Provide a worker-local self with postMessage, onmessage, and DOM-style message listener adapters.
• Support both postMessage(value, [transfer]) and postMessage(value, { transfer: [...] }) in child-to-parent and parent-to-child directions.
• Detach transferred ArrayBuffers while preserving cloned bytes.
• Preserve entangled MessagePort state and queued delivery across transfer.
• Surface revoked Blob worker URLs with causal module-resolution and worker-execution context.
• Fix Zig 0.17 optional/error propagation in corpus environment forwarding so the authoritative build graph compiles.
• Add permanent regression coverage for transfer ownership, Blob URL cleanup, and structured errors.

Verification:

• Position 4231: 3 passed, 0 failed, 0 todo, 0 unsupported.
• Positions 4230-4231: 60 passed, 0 failed, 0 todo, 0 unsupported.
• All focused permanent regressions pass.

Completed and pushed in bab20ca. The upstream transfer-overload file passes 3/3 and permanent Blob Worker lifecycle coverage is green.