fix: Align native skills frontmatter with install_ai_skills

[RbBtSn0w]

Follow-up to #1906.

Context

• Spec-kit now supports native skills for some agents (e.g. Codex/Kimi) where the template archive contains prebuilt SKILL.md files.
• We currently have multiple SKILL.md generators (release packaging, init-time install_ai_skills() conversion, and extension overrides). If their frontmatter contracts drift, we end up with inconsistent skills across agents.

What this PR changes

• Release packaging scripts: ensure native SKILL.md includes the same minimal frontmatter contract used by install_ai_skills() / extension overrides (adds compatibility and metadata.{author,source}) and adds a short note to keep generators in sync.
• Docs: update AGENTS.md to reflect Codex’s .agents/skills/ layout.
• Code comments: document the multi-generator technical debt near NATIVE_SKILLS_AGENTS and render_skill_command().

Impact

• Affects only release-packaged native skills output (template archives). No change to init-time install_ai_skills() conversion behavior.

Related discussions

• Hooks + Extensions: decouple logical command IDs from agent invocation (slash vs skills), and align skill naming rules #1918
• Skills generation drift: native skills vs install_ai_skills vs extension overrides (frontmatter + naming) #1919

Test plan

• bash -n .github/workflows/scripts/create-release-packages.sh
• CI will run the Python test suite.

[Copilot]

Pull request overview

This PR reduces “skills drift” by documenting that there are multiple SKILL.md generators in spec-kit and aligning the native (release-packaged) SKILL.md frontmatter shape with the schema used by init-time conversion and extension/preset overrides.

Changes:

• Document (in code comments) that SKILL.md can be generated via template packaging, install_ai_skills(), and extension/preset overrides, and that frontmatter keys must remain aligned.
• Update release packaging scripts to include compatibility and metadata (incl. metadata.source) in generated SKILL.md frontmatter.
• Update AGENTS.md to reflect Codex’s .agents/skills/ convention and invocation pattern.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/specify_cli/agents.py	Adds a technical-debt note clarifying multi-generator SKILL.md drift risk and schema alignment needs.
src/specify_cli/__init__.py	Documents the three SKILL.md generation paths and the minimum frontmatter schema to keep aligned.
AGENTS.md	Updates Codex directory convention to .agents/skills/ and clarifies skills invocation.
.github/workflows/scripts/create-release-packages.sh	Aligns native SKILL.md frontmatter by adding compatibility and metadata fields.
.github/workflows/scripts/create-release-packages.ps1	Mirrors the shell script’s SKILL.md frontmatter updates in the PowerShell packaging script.

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

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[mnriem]

Please address Copilot feedback. If not applicable, please explain why

[RbBtSn0w]

Addressed Copilot CR feedback:

• Updated the documented minimum SKILL.md frontmatter contract to include metadata.{author,source} (Python + packaging scripts).
• Clarified the render_skill_command() drift note to explicitly mention metadata.author and metadata.source.
• Updated AGENTS.md to move Codex out of the prompt-based exceptions list (now under skills-based exceptions).

Local verification:

• .venv/bin/python -m pytest -q (435 passed)
• bash -n .github/workflows/scripts/create-release-packages.sh

[RbBtSn0w]

@mnriem Copilot inline suggestions have been addressed and tests pass locally; could you please take another look?

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.

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