feat: add Codex support for extension command registration

[adri4nlm]

Summary

Add Codex support to extension command registration by adding a codex entry to CommandRegistrar.AGENT_CONFIGS in src/specify_cli/extensions.py.

Description

specify init --ai codex creates projects using .codex/prompts/, but specify extension add did not include Codex in the registrar agent map.

This change makes extension command installation target Codex projects as expected:

• directory: .codex/prompts
• format: markdown
• args placeholder: $ARGUMENTS
• file extension: .md

Testing

• Tested locally with uv run specify --help
• Ran existing tests with uv run pytest
• Tested with a sample project (if applicable)

uv run pytest result:

============================= 120 passed in 2.92s ==============================

AI Disclosure

• I did not use AI assistance for this contribution
• I did use AI assistance (describe below)

Used Codex to help prepare and validate this contribution. All final changes were reviewed by a human.

[Copilot]

Pull request overview

This PR adds Codex CLI to the CommandRegistrar.AGENT_CONFIGS map in extensions.py, enabling specify extension add to register extension commands into Codex projects (targeting .codex/prompts/ with Markdown format and $ARGUMENTS placeholder). The codex key was already present in AGENT_CONFIG in __init__.py and in the release packaging scripts, but was missing from the extension command registrar.

Changes:

• Adds a "codex" entry to CommandRegistrar.AGENT_CONFIGS with dir: .codex/prompts, format: markdown, args: $ARGUMENTS, and extension: .md.

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[Copilot]

The codebase follows a clear pattern of adding consistency tests whenever a new agent is added to CommandRegistrar.AGENT_CONFIGS. For example, kiro-cli has tests in both tests/test_extensions.py (lines 402–406) and tests/test_agent_config_consistency.py (lines 23–29) that verify the key is present, the directory is correct, and legacy keys are absent.

This PR does not add a test verifying that "codex" is present in CommandRegistrar.AGENT_CONFIGS with the expected "dir": ".codex/prompts". A test analogous to test_kiro_cli_agent_config_present should be added (e.g., in TestCommandRegistrar in tests/test_extensions.py) to pin this mapping and prevent regression.

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

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[mnriem]

Can you address the feedback by Copilot where applicable. If not applicable please describe why. Thanks!