feat(engineering): add autocad-expert and automotive-embedded skills

[chad848]

Summary

Adds two new engineering skills sourced from public GitHub skill repositories.

Checklist

• Target branch is dev (not main — PRs to main will be auto-closed)
• Skill has SKILL.md with valid YAML frontmatter (name, description, license)
• Scripts (if any) run with --help without errors
• No hardcoded API keys, tokens, or secrets
• No vendor-locked dependencies without open-source fallback
• Follows existing directory structure (domain/skill-name/SKILL.md)

Type of Change

• New skill
• Improvement to existing skill
• Bug fix
• Documentation
• Infrastructure / CI

Testing

[alirezarezvani]

Thanks for the submission. Quality review identified blocking issues — closing for now; please reopen after addressing the items below.

1. Broken markdown formatting (all 5 files). Every SKILL.md contains progressively-indented bullet artefacts (- - **X**, then - - **Y**, then - - **Z** …) that cascade and eventually break section headings, tables, and fenced code blocks (they render as nested list items instead). This affects autocad-expert, automotive-embedded, embedded-systems-engineer, misra-automotive-c, and solidworks-expert.

2. Layout mismatch. Current dev structure (post-#593) places sub-skills under engineering/skills/<skill-name>/SKILL.md with a plugin manifest. This PR drops bare SKILL.md files at engineering/<name>/ with no .claude-plugin/, no references/, no scripts/, no assets/ — the skills won't register.

3. Missing license in YAML frontmatter. PR's own checklist requires name, description, license. Only name + description are present.

4. Scope mismatch. PR title says 2 skills (autocad-expert + automotive-embedded); diff adds 5.

5. Source attribution. PR body says "sourced from public GitHub skill repositories" — please link the upstream repos so we can verify licensing compatibility and credit authors.

6. Quality bar. Per CLAUDE.md, every skill should "save users 40%+ time while improving consistency/quality by 30%+" via concrete workflows + scripts/ (Algorithm over AI). Current files are flat reference cheatsheets.

If you'd like to proceed: pick one skill at a time, restructure to engineering/skills/<name>/ with a plugin manifest, fix the markdown, add at least one Python tool or a concrete workflow, and resubmit.

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[alirezarezvani]

Closing this PR after audit (flagged "under audit" in #601). A few issues that would need to be resolved before this could land:

Scope mismatch
The PR title says "autocad-expert and automotive-embedded" but the diff actually adds 6 skills:

• autocad-expert, automotive-embedded, embedded-systems-engineer, llm-cost-optimizer, misra-automotive-c, solidworks-expert

Stale duplicate
engineering/llm-cost-optimizer/ already exists on dev (it credits you in the source). This PR replaces it with an older version that lacks the "Step 0: Classify Before You Ask" section and the proactive-trigger guidance the current version has. Merging would be a regression.

Broken markdown
Both autocad-expert/SKILL.md and automotive-embedded/SKILL.md have a cascading-bullet corruption that renders unreadably:

- **MISRA C:2012**: ...
- - **AUTOSAR C++14**: ...
- - - **CERT C**: ...
- - - - **Rule Enforcement**: ...

Missing repo skill structure
Each skill is a single SKILL.md. Per CLAUDE.md and CONVENTIONS.md, skills should ship scripts/, references/, and where appropriate assets/. None of the proposed skills include any of these.

Out-of-date base
The diff is 1856 files because the branch predates the #593 umbrella restructure. Even the "good" parts would need to be re-applied at the post-restructure path (engineering/skills/<name>/).

Suggestions if you'd like to resubmit

1. One PR per new skill (autocad-expert + solidworks-expert each as their own PR if you want both)
2. Drop llm-cost-optimizer from this set (already in dev with you credited)
3. Decide whether automotive-embedded, embedded-systems-engineer, and misra-automotive-c are three skills or one combined one — there's significant overlap between them
4. Fix the cascading-bullet markdown corruption in any reused content
5. Add scripts/ (Python CLI tool, stdlib only) and references/ per skill
6. Branch off current dev so you only diff your new content

Thanks for the contribution. Closing as-is.

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