[M4] Build the surface SDK, reference harness, and shared fault-injection corpus

Spec

M4 issue 41; surface §§11.3-11.8 and test strategy.

Current evidence

No web/surface-sdk, surface fixture corpus, or cross-language reference harness exists.

Deliverables

JS/TS SDK for frozen v0; reference host; revision/resync/action/lifecycle helpers; deterministic Rust/JS/Apple fixtures; gap/oversize/delay/crash/spoof fault injection; authoring docs.

Acceptance

Same corpus passes Rust, Node and Apple; proves mount/ready/snapshot, gap/resync, slow convergence, action refusal/cancel, teardown, and no bridge/window.nostr/direct-network authority.

Dependencies

Surface contract/protocol, binding registry and surface actions.

Global constraints

• Exact pinned baseline; no dependency movement in this issue.
• ~/Work/nmp is read-only and the NMP public facade is the only integration boundary.
• Add teardown/resource counters and independent adversarial review.

Start by reading the Surface contract/protocol, binding registry, and surface actions, then confirm the exact pinned baseline and NMP public-facade boundary. The work should produce the JS/TS SDK, reference host, shared deterministic Rust/JS/Apple fixture corpus, and fault-injection coverage. Done means the corpus passes on Rust, Node, and Apple and covers the listed lifecycle, resync, refusal, teardown, and authority constraints.