Port PR guidelines from sdk-typescript

[zastrowm]

Description

Port PR guidelines from sdk-typescript so that agents & contributors can use them. Updated the PR.md with appropriate python examples and referenced the doc from other files.

Related files from sdk-typescript:

• https://github.com/strands-agents/sdk-typescript/blob/main/docs/PR.md
• https://github.com/strands-agents/sdk-typescript/blob/main/AGENTS.md

Type of Change

Documentation update

Testing

How have you tested the change? Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli

• I ran hatch run prepare

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

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By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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