chore: rework prompt engineer agent to support agent skills

[fbeaudoincoveo]

This PR introduces several new files, but it is very low-risk:

• We're adding a core set of meta-skills (creating-skills, creating-prompts, creating-instructions, creating-agents) that will be discoverable / usable by our AI agents. Note that the skills are in a .claude directory. I'm putting them there for maximum compatibility with AI tools (.claude/skills will be discoverable by GH Copilot, OpenCode, and ClaudeCode agents alike... and probably others too).
• We're adding a PromptEngineerV2 agent that leverages these meta-skills. The agent also has a series of test scenarios to ensure it's working as intended.
• We're keeping the PromptEngineerV1 untouched for now. The PromptEngineerV2 is essentially a refactored / improved version of it that leverages meta skills instead of having its instructions inline.
• We're deleting the old prompt-engineer chatmode (chatmodes are deprecated, and this was a primitive attempt that was already made obsolete by the PromptEngineerV1 agent).

I also completely rewrote our AGENTS.md and moved it to the root of the project. It was a mess and we were using it wrong.

Finally, I added / optimized an opencode.json file (+ instructions in our internal-docs folder) for those who would like to use it ;)

#6917
https://coveord.atlassian.net/browse/KIT-5367

[Copilot]

Pull request overview

This PR reworks the prompt engineer agent to support the new Agent Skills concept and completely rewrites the AGENTS.md documentation. The changes introduce four new comprehensive skills for creating prompts, skills, agents, and instructions, along with their associated validation and initialization scripts.

Key changes:

• Introduces the Agent Skills standard (agentskills.io) with portable, agent-discoverable capabilities
• Creates four new skills: creating-skills, creating-prompts, creating-instructions, and creating-agents
• Updates prompt-engineer-v2 agent to orchestrate these skills for artifact creation
• Rewrites AGENTS.md from a verbose agent catalog to a concise operational reference

Reviewed changes

Copilot reviewed 34 out of 34 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
.github/skills/creating-skills/scripts/quick_validate.mjs	Validates skill structure and frontmatter per Agent Skills spec
.github/skills/creating-skills/scripts/package_skill.mjs	Packages skills into .skill tarball format
.github/skills/creating-skills/scripts/init_skill.mjs	Scaffolds new skill directory with template files
.github/skills/creating-skills/references/*.md	Reference documentation for workflows, output patterns, best practices, and spec
.github/skills/creating-skills/SKILL.md	Main skill definition for creating Agent Skills
.github/skills/creating-prompts/scripts/*.mjs	Validation and initialization for VS Code Copilot prompts
.github/skills/creating-prompts/references/*.md	Prompt authoring guidance including workflows, templates, best practices, and spec
.github/skills/creating-prompts/SKILL.md	Main skill definition for creating prompts
.github/skills/creating-instructions/scripts/*.mjs	Validation and initialization for custom instructions
.github/skills/creating-instructions/references/*.md	Instruction authoring guidance including naming, examples, best practices, and spec
.github/skills/creating-instructions/SKILL.md	Main skill definition for creating instructions
.github/skills/creating-agents/scripts/*.mjs	Validation and initialization for custom agents
.github/skills/creating-agents/references/*.md	Agent authoring guidance including frontmatter, patterns, agentic coding, and spec
.github/skills/creating-agents/SKILL.md	Main skill definition for creating agents
.github/agents/prompt-engineer-v2.agent.md	Updated agent with skill-based workflow and clarification stage
.github/agents/examples/prompt-engineer-v2-examples.md	Comprehensive test scenarios for the updated agent
.github/AGENTS.md	Rewritten as concise operational reference instead of verbose catalog
.cspell.json	Added terminology: agentic, OOXML, pdfs

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[github-actions]

🔗 Scratch Orgs ready to test this PR:

• ✅ LWS Enabled: Open Org
• ✅ LWS Disabled: Open Org

[Copilot]

@fbeaudoincoveo I've opened a new pull request, #6923, to work on those changes. Once the pull request is ready, I'll request review from you.

[Copilot]

@fbeaudoincoveo I've opened a new pull request, #6924, to work on those changes. Once the pull request is ready, I'll request review from you.