Stdlib: stream_context_create() — VM + LLVM JIT/AOT

[PurHur]

Summary

Implement stream_context_create() for full PHP parity: VM, LLVM JIT, and AOT/self-host where applicable.

Create stream contexts for fopen wrappers and HTTP.

Context

• Not in docs/capabilities.md (or JIT-deferred only).
• North Star 1 #1044 · Self-host #1056
• Audit: php script/audit-stdlib-jit.php

Acceptance criteria

• stream_context_create() in builtin tables / SelfHostBuiltinPolicy
• VM + PHPUnit (compliance PHPT or unit test)
• LLVM JIT lowering (or explicit deferral with issue link)
• docs/capabilities.md row updated (regenerate matrix)

Related

Stdlib wave 2 tracker #1237 (closed; prior items largely landed).

[PurHur]

JIT lowering scaffold in JitStreamContextCreate.php (PR incoming); VM-only until enabled.