[CI] : Add documentation for current CI Pipeline

[Jenish-1235]

Current Behavior

There is no single document explaining the current CI pipeline in Music Blocks (workflows, triggers, and coverage). Contributors must inspect workflow files manually.

Desired Behavior

Add a concise CI documentation file so contributors can quickly understand what runs in CI and what gaps exist.

Implementation

Create Docs/ci-pipeline.md with:

• list of current workflows
• trigger summary (push/PR/schedule/manual)
• short purpose of each workflow
• key known issues and immediate fixes

Acceptance Tests

• Docs/ci-pipeline.md added
• All current CI workflows documented
• Trigger summary included
• Known issues listed clearly

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Checklist

• I have read and followed the project's code of conduct.
• I have searched for similar issues before creating this one.
• I have provided all the necessary information to understand and reproduce the issue.
• I am willing to contribute to the resolution of this issue.

[MSIVAPAPARAO13]

@Jenish-1235 Hello, I would like to work on this issue.
Could you please confirm if I can proceed?

[Jenish-1235]

There's already a Open PR, I am working on it.