feat(engineering): add browser-automation and spec-driven-workflow skills

browser-automation (564-line SKILL.md, 3 scripts, 3 references):
- Web scraping, form filling, screenshot capture, data extraction
- Anti-detection patterns, cookie/session management, dynamic content
- scraping_toolkit.py, form_automation_builder.py, anti_detection_checker.py
- NOT testing (that's playwright-pro) — this is automation & scraping

spec-driven-workflow (586-line SKILL.md, 3 scripts, 3 references):
- Spec-first development: write spec BEFORE code
- Bounded autonomy rules, 6-phase workflow, self-review checklist
- spec_generator.py, spec_validator.py, test_extractor.py
- Pairs with tdd-guide for red-green-refactor after spec

Updated engineering plugin.json (31 → 33 skills).
Added both to mkdocs.yml nav and generated docs pages.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mkdocs.yml

@@ -174,6 +174,7 @@ nav:
       - "Agent Workflow Designer": skills/engineering/agent-workflow-designer.md
       - "API Design Reviewer": skills/engineering/api-design-reviewer.md
       - "API Test Suite Builder": skills/engineering/api-test-suite-builder.md
+      - "Browser Automation": skills/engineering/browser-automation.md
       - "Changelog Generator": skills/engineering/changelog-generator.md
       - "CI/CD Pipeline Builder": skills/engineering/ci-cd-pipeline-builder.md
       - "Codebase Onboarding": skills/engineering/codebase-onboarding.md
@@ -195,6 +196,7 @@ nav:
       - "Runbook Generator": skills/engineering/runbook-generator.md
       - "Skill Security Auditor": skills/engineering/skill-security-auditor.md
       - "Skill Tester": skills/engineering/skill-tester.md
+      - "Spec-Driven Workflow": skills/engineering/spec-driven-workflow.md
       - "Tech Debt Tracker": skills/engineering/tech-debt-tracker.md
       - "Terraform Patterns": skills/engineering/terraform-patterns.md
       - "Helm Chart Builder": skills/engineering/helm-chart-builder.md