fix: retire legacy command shims from default surface

legacy-command-shims/commands/tdd.md

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+---
+description: Legacy slash-entry shim for the tdd-workflow skill. Prefer the skill directly.
+---
+
+# TDD Command (Legacy Shim)
+
+Use this only if you still invoke `/tdd`. The maintained workflow lives in `skills/tdd-workflow/SKILL.md`.
+
+## Canonical Surface
+
+- Prefer the `tdd-workflow` skill directly.
+- Keep this file only as a compatibility entry point.
+
+## Arguments
+
+`$ARGUMENTS`
+
+## Delegation
+
+Apply the `tdd-workflow` skill.
+- Stay strict on RED -> GREEN -> REFACTOR.
+- Keep tests first, coverage explicit, and checkpoint evidence clear.
+- Use the skill as the maintained TDD body instead of duplicating the playbook here.
+})
+```
+
+## Step 3: Run Tests - Verify FAIL
+
+```bash
+npm test lib/liquidity.test.ts
+
+FAIL lib/liquidity.test.ts
+  ✕ should return high score for liquid market (2 ms)
+    Error: Not implemented
+
+1 test failed, 0 passed
+```
+
+PASS: Tests fail as expected. Ready to implement.
+
+## Step 4: Implement Minimal Code (GREEN)
+
+```typescript
+// lib/liquidity.ts
+export function calculateLiquidityScore(market: MarketData): number {
+  // Handle zero volume edge case
+  if (market.totalVolume === 0) {
+    return 0
+  }
+
+  // Calculate component scores (0-100 scale)
+  const volumeScore = Math.min(market.totalVolume / 1000, 100)
+  const spreadScore = Math.max(100 - (market.bidAskSpread * 1000), 0)
+  const traderScore = Math.min(market.activeTraders / 10, 100)
+
+  // Recent activity bonus
+  const hoursSinceLastTrade = (Date.now() - market.lastTradeTime.getTime()) / (1000 * 60 * 60)
+  const recencyScore = Math.max(100 - (hoursSinceLastTrade * 10), 0)
+
+  // Weighted average
+  const score = (
+    volumeScore * 0.4 +
+    spreadScore * 0.3 +
+    traderScore * 0.2 +
+    recencyScore * 0.1
+  )
+
+  return Math.min(Math.max(score, 0), 100) // Clamp to 0-100
+}
+```
+
+## Step 5: Run Tests - Verify PASS
+
+```bash
+npm test lib/liquidity.test.ts
+
+PASS lib/liquidity.test.ts
+  ✓ should return high score for liquid market (3 ms)
+  ✓ should return low score for illiquid market (2 ms)
+  ✓ should handle edge case: zero volume (1 ms)
+
+3 tests passed
+```
+
+PASS: All tests passing!
+
+## Step 6: Refactor (IMPROVE)
+
+```typescript
+// lib/liquidity.ts - Refactored with constants and better readability
+const WEIGHTS = {
+  VOLUME: 0.4,
+  SPREAD: 0.3,
+  TRADERS: 0.2,
+  RECENCY: 0.1,
+} as const
+
+const SCALE_FACTORS = {
+  VOLUME: 1000,
+  SPREAD: 1000,
+  TRADERS: 10,
+  RECENCY_PENALTY: 10,
+} as const
+
+function clamp(value: number, min: number, max: number): number {
+  return Math.min(Math.max(value, min), max)
+}
+
+export function calculateLiquidityScore(market: MarketData): number {
+  if (market.totalVolume === 0) return 0
+
+  const volumeScore = Math.min(market.totalVolume / SCALE_FACTORS.VOLUME, 100)
+  const spreadScore = clamp(100 - (market.bidAskSpread * SCALE_FACTORS.SPREAD), 0, 100)
+  const traderScore = Math.min(market.activeTraders / SCALE_FACTORS.TRADERS, 100)
+
+  const hoursSinceLastTrade = (Date.now() - market.lastTradeTime.getTime()) / (1000 * 60 * 60)
+  const recencyScore = clamp(100 - (hoursSinceLastTrade * SCALE_FACTORS.RECENCY_PENALTY), 0, 100)
+
+  const weightedScore =
+    volumeScore * WEIGHTS.VOLUME +
+    spreadScore * WEIGHTS.SPREAD +
+    traderScore * WEIGHTS.TRADERS +
+    recencyScore * WEIGHTS.RECENCY
+
+  return clamp(weightedScore, 0, 100)
+}
+```
+
+## Step 7: Verify Tests Still Pass
+
+```bash
+npm test lib/liquidity.test.ts
+
+PASS lib/liquidity.test.ts
+  ✓ should return high score for liquid market (3 ms)
+  ✓ should return low score for illiquid market (2 ms)
+  ✓ should handle edge case: zero volume (1 ms)
+
+3 tests passed
+```
+
+PASS: Refactoring complete, tests still passing!
+
+## Step 8: Check Coverage
+
+```bash
+npm test -- --coverage lib/liquidity.test.ts
+
+File           | % Stmts | % Branch | % Funcs | % Lines
+---------------|---------|----------|---------|--------
+liquidity.ts   |   100   |   100    |   100   |   100
+
+Coverage: 100% PASS: (Target: 80%)
+```
+
+PASS: TDD session complete!
+```
+
+## TDD Best Practices
+
+**DO:**
+- PASS: Write the test FIRST, before any implementation
+- PASS: Run tests and verify they FAIL before implementing
+- PASS: Write minimal code to make tests pass
+- PASS: Refactor only after tests are green
+- PASS: Add edge cases and error scenarios
+- PASS: Aim for 80%+ coverage (100% for critical code)
+
+**DON'T:**
+- FAIL: Write implementation before tests
+- FAIL: Skip running tests after each change
+- FAIL: Write too much code at once
+- FAIL: Ignore failing tests
+- FAIL: Test implementation details (test behavior)
+- FAIL: Mock everything (prefer integration tests)
+
+## Test Types to Include
+
+**Unit Tests** (Function-level):
+- Happy path scenarios
+- Edge cases (empty, null, max values)
+- Error conditions
+- Boundary values
+
+**Integration Tests** (Component-level):
+- API endpoints
+- Database operations
+- External service calls
+- React components with hooks
+
+**E2E Tests** (use `/e2e` command):
+- Critical user flows
+- Multi-step processes
+- Full stack integration
+
+## Coverage Requirements
+
+- **80% minimum** for all code
+- **100% required** for:
+  - Financial calculations
+  - Authentication logic
+  - Security-critical code
+  - Core business logic
+
+## Important Notes
+
+**MANDATORY**: Tests must be written BEFORE implementation. The TDD cycle is:
+
+1. **RED** - Write failing test
+2. **GREEN** - Implement to pass
+3. **REFACTOR** - Improve code
+
+Never skip the RED phase. Never write code before tests.
+
+## Integration with Other Commands
+
+- Use `/plan` first to understand what to build
+- Use `/tdd` to implement with tests
+- Use `/build-fix` if build errors occur
+- Use `/code-review` to review implementation
+- Use `/test-coverage` to verify coverage
+
+## Related Agents
+
+This command invokes the `tdd-guide` agent provided by ECC.
+
+The related `tdd-workflow` skill is also bundled with ECC.
+
+For manual installs, the source files live at:
+- `agents/tdd-guide.md`
+- `skills/tdd-workflow/SKILL.md`