Add automated QA reporter to validate all samples against the v0.9 schema

[selamw1]

We currently lack real-time automated insight into whether our sample component configurations (like custom layouts or interactive responses) stay synchronized with new specification enhancements.

This PR generates scripts/qa_report.py to automatically validate sample(currently 11) JSON configurations against the A2UI v0.9 specification schema. It also adds a scheduled GitHub Action for periodic verification.

Solution

• Built scripts/qa_report.py, an automated Python script validating internal mocks against core SDK boundaries (like v0.9).
• Configured .github/workflows/periodic-qa.yml for automatic CI gatekeeping.

Verification Plan

• Validated the 11 samples locally, and all passed against the v0.9 schema.

- [x] I signed the [CLA].
- [x] I read the [Contributors Guide].
- [x] I read the [Style Guide].
- [x] I have added updates to the [CHANGELOG].
- [x] I updated/added relevant documentation.
- [x] My code changes (if any) have tests.

[gemini-code-assist]

Code Review

This pull request introduces a new QA report script, scripts/qa_report.py, which validates A2UI samples against the v0.9 specification and generates a Markdown report. The review feedback identifies several improvement opportunities, including adhering to PEP 8 blank line conventions, verifying file types during directory traversal, enhancing the clarity of error messages in the report, and ensuring consistent UTF-8 encoding for file output.