[New Skill]: Azure Storage migration skill (S3 to Blob)

### Skill Name

convert-s3-to-azure-blob

### Contacts

Kyle Knapp (kyleknap), Anthony Howe (anhowe)

### Intended Agent Scenarios

When a customer has an existing application that talks to Amazon S3, this skill helps them convert it to Azure Blob Storage and assists validating the conversion. Ideally, this skill will eventually help code conversions for all languages that Azure Storage SDK supports (e.g., .NET, Java, Python, Rust, Javascript C++, Go).

## Rationale

While most cloud storage services have an S3-compatible endpoint (i.e., where you can point an AWS SDK at to make work with a non-AWS provider), Azure Blob Storage does not have an S3-compatible endpoint, and its APIs/concepts do not map cleanly to S3 APIs/concepts. So, this skill is intended to streamline/guide a customer through how they can make their S3 app now talk to Blob.

## Example tasks
* "Convert this S3 client code to Azure Blob Storage."
* "Validate that I've migrated my app from S3 to Azure Blob correctly" (note: initial conversion by skill would include validation as well, but they may want to rerun validation steps after more iterations)

### Timeline

Q3 2026 (i.e., July-September 2026)

### Additional Context

_No response_

No files, tests, or entry points are named. Start by locating existing agent skills and their tests, then compare their structure with the requested convert-s3-to-azure-blob scenarios. Done means the skill can guide S3-to-Blob conversions and validate migrated applications, with its supported language scope defined.

Written by the indexing model from the issue text.