Rename internal prompting skill to version-neutral codex-prompting

[Copilot]

The internal prompting skill was named gpt-5-4-prompting, which made generic prompt-engineering guidance look tied to an outdated model version. This change renames the skill to codex-prompting and updates all internal references while leaving runtime model selection behavior unchanged.

• Skill rename

  • Moves plugins/codex/skills/gpt-5-4-prompting/ to plugins/codex/skills/codex-prompting/
  • Preserves all existing reference documents under the new path

• Version-neutral skill docs

  • Updates skill metadata from name: gpt-5-4-prompting to name: codex-prompting
  • Replaces version-specific wording such as GPT-5.4 / Codex or GPT-5.4 with neutral Codex-focused language
  • Keeps the technical prompt-engineering guidance unchanged

• Consumer updates

  • Switches plugins/codex/agents/codex-rescue.md to the new skill name in both frontmatter and body text
  • Switches plugins/codex/skills/codex-cli-runtime/SKILL.md to reference codex-prompting

• Test updates

  • Updates tests/commands.test.mjs to read the renamed skill paths
  • Keeps the existing content assertions intact, only adjusting references affected by the rename

Example of the internal rename:

skills:
  - codex-cli-runtime
  - codex-prompting

[ygCEO]

OK