docs: make execution report example portable

[Pigbibi]

Summary

• replace the deployment-specific execution-report prefix in .env.example with an explicit public GCS placeholder
• add one focused contract test for the exact placeholder and URI structure
• preserve every other .env.example line unchanged

Scope

.env.example and its focused test only. No workflow, runtime, verifier, permission, trigger, dependency, deployment, or live behavior changes.

Validation

• python3 -m pytest -q tests/test_env_example.py (1 passed)
• python3 -m ruff check .
• python3 -m compileall -q .
• non-target .env.example identity check
• git diff HEAD^ --check

Full suite result: 2 failed, 178 passed. The same two failures existed on the clean baseline and are unrelated to this sample-only change:

• tests/test_shared_chat_id_fallback.py::SharedChatIdTests::test_global_telegram_chat_id_is_used
• tests/test_uv_dependency_workflow.py::test_ci_and_docker_use_uv_lock

Risk

Low. The example file is not loaded by tracked runtime or workflow code; actual execution-report configuration continues to come from runtime environment or repository variables.

[github-actions]

🤖 Codex PR Review

✅ Merge allowed: No issues found

---

Review by Codex PR Review bot • PR