Update LICENSE copyright and add AI attribution instructions

[jerrysxie]

This PR applies two org-wide standardisation changes
(ref: OpenDevicePartnership/embedded-rust-template#20):

1. LICENSE – normalise the copyright line to:
   Copyright (c) Open Device Partnership and Contributors

2. .github/copilot-instructions.md – add the Commit Messages and
   AI Attribution sections so every repo carries consistent guidance
   for contributors and AI agents.

[Copilot]

Pull request overview

This PR applies org-wide standardization updates by normalizing the MIT LICENSE copyright holder line and adding repository-wide contributor/agent guidance for commit message formatting and AI attribution.

Changes:

• Updated LICENSE to use the standardized copyright line (“Open Device Partnership and Contributors”).
• Added .github/copilot-instructions.md documenting commit message conventions and a required Assisted-by trailer for AI-assisted commits.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
LICENSE	Normalizes the MIT license copyright line to the org standard.
.github/copilot-instructions.md	Adds standard guidance for commit messages and AI attribution trailers.

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