fix(ci): grant AI review contents write permission

[zhongkechen]

Summary

• grant the reusable AI review workflow the contents: write permission required by its v0.3.0 telemetry job
• add a regression test for the caller permission contract
• run the GitHub script tests when the AI review workflow changes

This fixes the startup failure in https://github.com/aws/aws-durable-execution-sdk-python/actions/runs/33423069291.

Note

This PR's own AI PR Review run is expected to have the same startup failure
because pull_request_target evaluates the workflow from the base branch.
The corrected permission takes effect after this change reaches main.

Validation

• parsed the modified workflows with PyYAML
• ran the new regression assertion directly
• ran git diff --check
• ran .github/scripts/lintcommit.py

The full script-test command was not run locally because pytest is not installed in the workspace; the updated Test GitHub Scripts workflow will run it in CI.