Add public readiness docs for Node SDK

[negillett]

Summary

• Add TRADEMARK.md and link trademark policy in CONTRIBUTING.md.
• Expand README.md with install, verify, test, release, support, and CI badge.
• Align with Stage 1 public repository readiness checklist.

Test plan

• See repo-specific gates in checkpoint (docs-only where applicable).

Review

• Documentation-only diff; no blocking findings after internal review.

[cursor]

PR Summary

Low Risk
Docs-only changes that don’t affect runtime behavior; risk is limited to potential confusion if guidance or links are incorrect.

Overview
Improves public repo readiness documentation by expanding README.md with a CI badge plus sections for install, verification/testing, release process, documentation/support links, and updated license references.

Adds a new TRADEMARK.md policy and links it from CONTRIBUTING.md, clarifying that Apache 2.0 does not grant a trademark license for “IntentProof” marks.

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