feat(http): add bounded request and callable SSE clients

[fffonion]

Summary

• Provides bounded buffered HTTP requests and callable SSE streaming.
• Preserves address policy, redirect revalidation, response/item/total byte limits, deadlines, cancellation, cleanup, and callback backpressure.
• Keeps the generic stream pump crate-internal and moves its tests into the VM unit-test module.
• Removes the unconsumed HTTP WebSocket builtin, dependencies, configuration, tests, docs, and public HostStream* embedding surface.

Stack

• Base: feat(compiler): finalize frame-local typing and ownership #24
• Tip of the seven-layer stack

Verification

• HTTP host: 16 passed
• SSE: 17 passed
• Internal stream: 25 passed
• Host binding: 10 passed
• Feature gating: 2 passed
• Final workspace all-features, no-std, wasm, fmt, diff-check, and strict Clippy passed

Supersedes

• feat(http): add a bounded cancellable host client #13
• fix(http): enforce address and response deadline policy #17
• HTTP portions of refactor(host): isolate host-owned policies and async IO #20