Add Task 9 environment variables report workflow and report-generation scripts

[Testtesttestestes]

Motivation

• Add a new automated report for practical task 9 to capture environment variables behavior and produce a PDF report.
• Integrate the new task into the repository's workflows list and make the report author configurable via workflow environment.

Description

• Add a new GitHub Actions workflow /.github/workflows/task9-env-vars-report.yml that runs on workflow_dispatch and on pushes to the workflow and report script paths, sets REPORT_AUTHOR, installs python3-pil, runs the report script, and uploads reports/task9/report.pdf as an artifact.
• Add scripts/task9_env_vars_report.sh which creates reports/task9, generates env_info.sh and child.sh, captures command outputs to logs, converts logs to PNG using scripts/text_to_png.py, builds report.json, and invokes scripts/build_pdf_report.py to produce report.pdf.
• Update README.md to reflect that there are now 9 workflows and add Task 9 - Environment variables report to the list.

Testing

• No automated tests were executed as part of this PR; the new workflow is configured to run on manual dispatch (workflow_dispatch) or on relevant file changes and will produce artifacts when executed.

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Codex Task