docs: verify Codex write access

[ranade-oss]

Motivation

• Add a temporary artifact to confirm the automated agent/tool can create and commit files in the repository.

Description

• Add docs/codex-write-access-test.md containing the single line Temporary Codex write-access verification. to verify write capability.

Testing

• Ran git diff --check, validated file content with test "$(cat docs/codex-write-access-test.md)" = "Temporary Codex write-access verification.", inspected git status --short --branch, and checked git show --stat for the commit; all commands succeeded.

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Codex Task