Add OSS compliance deliverables per Legal approval (MIT retained)

[larabasegg]

Summary

Implements the Prosus Legal ruling for the ClawHive open source release.

Legal status: ✅ APPROVED — Keep MIT License (conservative approach).
MIT is already business-friendly; relicensing is not required. Add compliance files without changing the license. External contractor (Datacation) contributions are respected.

This PR adds the deliverables Legal requested and resolves the open items from the earlier CLAWHIVE_COMPLIANCE_AUDIT.md.

Changes

Item	Status
LICENSE	✅ MIT kept as-is; copyright line updated to Copyright © 2026 MIH AI B.V. and contributors
CONTRIBUTING.md	✅ Full CLA added — copyright assignment to MIH AI B.V., contributions licensed under MIT, originality + no-conflicting-obligations. Existing dev-setup guide preserved (no hybrid/self-contradictory text)
README	✅ MIT license badge + License section with Copyright © 2026 MIH AI B.V. and contributors
NOTICE	✅ Minimal third-party attribution (all deps permissive — MIT/Apache/ISC/BSD/Python-2.0/BlueOak; OpenClaw runtime confirmed MIT)

Source file headers

Per Legal's rule #4 (new MIH files → MIT header; existing files → do not modify):

• No headers added. This PR creates no new source files, and all existing files are left untouched to respect original/contractor (Datacation) contributions.

MIT-style header for future new MIH files (for reference, not applied here):

# Copyright © 2026 MIH AI B.V.
# Licensed under the MIT License.
# See LICENSE file in the project root for full license information.

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