Add exact ratio distribution for deterministic test data generation

[layoutd]

NOTE: This PR branches from #182 and will need merge conflict resolution with #184 and #185 (all modify the batch() method). The conflicts are trivial - just combining initialization calls.

Builds on: #182

Summary

Adds exact ratio distribution for coupon and refund generation in batch mode, eliminating variance from probabilistic distribution.

Current Behavior (Probabilistic)

With 100 orders at 0.5 coupon ratio:

• ❌ Get 45-55 coupons (varies due to random chance)
• ❌ Can't predict exact counts for testing

New Behavior (Deterministic)

With 100 orders at 0.5 coupon ratio:

• ✅ Get exactly 50 coupons (pre-calculated distribution)
• ✅ Predictable counts for testing and verification

Implementation

Coupon Distribution

Pre-generates an array of boolean flags:

// 100 orders, 0.5 ratio → exactly 50 true, 50 false
[true, true, ..., false, false]
shuffle($flags);

Odd number handling: Uses round() for non-exact splits:

• 11 orders @ 0.5 ratio → round(11 × 0.5) = round(5.5) = 6 with coupons, 5 without

Refund Distribution

Pre-generates refund type flags with exact split using integer constants for memory efficiency:

// Integer constants for memory optimization
const REFUND_TYPE_NONE = 0;
const REFUND_TYPE_FULL = 1;
const REFUND_TYPE_PARTIAL = 2;
const REFUND_TYPE_MULTI = 3;

// 100 orders, 0.4 refund ratio → 40 refunds total:
// - 20 full (50%)
// - 10 single partial (25%)
// - 10 multi-partial (25%)
[1, 1, ..., 2, 2, ..., 3, 3, ..., 0, 0, ...]
shuffle($flags);

Odd number handling: Remainder goes to multi-partial:

• 11 orders @ 0.4 ratio → 4 total refunds (rounded)
  • round(4 × 0.5) = 2 full
  • round(4 × 0.25) = 1 partial
  • 4 - 2 - 1 = 1 multi (remainder)
  • 11 - 4 = 7 none

Memory efficiency: For 20,000 orders, integers use ~160 KB vs strings ~160-320 KB, plus better CPU cache locality.

Benefits

1. Deterministic Testing - Exact ratios make test verification trivial
2. No Variance - Eliminates "it's random so ¯_(ツ)_/¯" excuse
3. Backwards Compatible - Single orders still use probabilistic approach
4. Memory Efficient - Integer constants instead of strings for large batches
5. Performance - No impact (simple array operations with good cache locality)

Testing

# Test exact coupon ratio
wp wc generate orders 100 --coupon-ratio=0.5
# Result: EXACTLY 50 orders with coupons

# Test odd numbers (rounding)
wp wc generate orders 11 --coupon-ratio=0.5
# Result: EXACTLY 6 orders with coupons (5.5 rounds up)

# Test exact refund ratio  
wp wc generate orders 100 --status=completed --refund-ratio=0.4
# Result: EXACTLY 20 full, 10 partial, 10 multi-partial refunds

[Copilot]

Pull Request Overview

This PR implements exact ratio distribution for batch order generation to ensure that coupon and refund ratios are applied deterministically in batch mode rather than probabilistically. This addresses accuracy issues where random application could deviate from specified ratios.

Key changes:

• Added pre-generated flag arrays for exact ratio distribution in batch mode
• Introduced refund type constants (NONE, FULL, PARTIAL, MULTI) for memory-efficient operations
• Modified coupon and refund logic to use deterministic flags in batch mode while maintaining backward compatibility with probabilistic single-order generation

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[Copilot]

Pull Request Overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 5 comments.

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