feat: add 33 skills from vudovn/antigravity-kit

- Added: api-patterns, app-builder, architecture, bash-linux, behavioral-modes,
  clean-code, code-review-checklist, database-design, deployment-procedures,
  docker-expert, documentation-templates, game-development, geo-fundamentals,
  i18n-localization, lint-and-validate, mobile-design, nestjs-expert,
  nextjs-best-practices, nodejs-best-practices, parallel-agents,
  performance-profiling, plan-writing, powershell-windows, prisma-expert,
  python-patterns, react-patterns, red-team-tactics, seo-fundamentals,
  server-management, tailwind-patterns, tdd-workflow, typescript-expert,
  vulnerability-scanner
- Updated README: skill count 179 → 223
- Added credit for vudovn/antigravity-kit (MIT License)

Source: https://github.com/vudovn/antigravity-kit

skills/tdd-workflow/SKILL.md

@@ -0,0 +1,149 @@
+---
+name: tdd-workflow
+description: Test-Driven Development workflow principles. RED-GREEN-REFACTOR cycle.
+allowed-tools: Read, Write, Edit, Glob, Grep, Bash
+---
+
+# TDD Workflow
+
+> Write tests first, code second.
+
+---
+
+## 1. The TDD Cycle
+
+```
+🔴 RED → Write failing test
+    ↓
+🟢 GREEN → Write minimal code to pass
+    ↓
+🔵 REFACTOR → Improve code quality
+    ↓
+   Repeat...
+```
+
+---
+
+## 2. The Three Laws of TDD
+
+1. Write production code only to make a failing test pass
+2. Write only enough test to demonstrate failure
+3. Write only enough code to make the test pass
+
+---
+
+## 3. RED Phase Principles
+
+### What to Write
+
+| Focus | Example |
+|-------|---------|
+| Behavior | "should add two numbers" |
+| Edge cases | "should handle empty input" |
+| Error states | "should throw for invalid data" |
+
+### RED Phase Rules
+
+- Test must fail first
+- Test name describes expected behavior
+- One assertion per test (ideally)
+
+---
+
+## 4. GREEN Phase Principles
+
+### Minimum Code
+
+| Principle | Meaning |
+|-----------|---------|
+| **YAGNI** | You Aren't Gonna Need It |
+| **Simplest thing** | Write the minimum to pass |
+| **No optimization** | Just make it work |
+
+### GREEN Phase Rules
+
+- Don't write unneeded code
+- Don't optimize yet
+- Pass the test, nothing more
+
+---
+
+## 5. REFACTOR Phase Principles
+
+### What to Improve
+
+| Area | Action |
+|------|--------|
+| Duplication | Extract common code |
+| Naming | Make intent clear |
+| Structure | Improve organization |
+| Complexity | Simplify logic |
+
+### REFACTOR Rules
+
+- All tests must stay green
+- Small incremental changes
+- Commit after each refactor
+
+---
+
+## 6. AAA Pattern
+
+Every test follows:
+
+| Step | Purpose |
+|------|---------|
+| **Arrange** | Set up test data |
+| **Act** | Execute code under test |
+| **Assert** | Verify expected outcome |
+
+---
+
+## 7. When to Use TDD
+
+| Scenario | TDD Value |
+|----------|-----------|
+| New feature | High |
+| Bug fix | High (write test first) |
+| Complex logic | High |
+| Exploratory | Low (spike, then TDD) |
+| UI layout | Low |
+
+---
+
+## 8. Test Prioritization
+
+| Priority | Test Type |
+|----------|-----------|
+| 1 | Happy path |
+| 2 | Error cases |
+| 3 | Edge cases |
+| 4 | Performance |
+
+---
+
+## 9. Anti-Patterns
+
+| ❌ Don't | ✅ Do |
+|----------|-------|
+| Skip the RED phase | Watch test fail first |
+| Write tests after | Write tests before |
+| Over-engineer initial | Keep it simple |
+| Multiple asserts | One behavior per test |
+| Test implementation | Test behavior |
+
+---
+
+## 10. AI-Augmented TDD
+
+### Multi-Agent Pattern
+
+| Agent | Role |
+|-------|------|
+| Agent A | Write failing tests (RED) |
+| Agent B | Implement to pass (GREEN) |
+| Agent C | Optimize (REFACTOR) |
+
+---
+
+> **Remember:** The test is the specification. If you can't write a test, you don't understand the requirement.