Optimize order date generation

[layoutd]

Replaces inefficient date array building with direct timestamp calculation.

Builds on: #182

Problem

For each order, the old code built an array of all dates in the range (e.g., 664 dates for 2 years), then used array_rand(). For 500 orders over 2 years, this created 332,000 unnecessary date strings.

Solution

Calculate random offset directly using timestamps instead of building arrays.

Impact

• Instant date calculation vs building 664-element arrays per order
• Eliminates wasted memory allocation
• Same uniform random distribution
• Orders are created in chronological order (smaller order ID = earlier order)

Tests

Test 1: Batch generation with date range produces chronological orders

wp wc generate orders 10 --date-start=2024-01-01 --date-end=2024-12-31

Expected: Order dates should be in ascending or equal order (no date inversions where later ID has earlier date)

Test 2: Same-day date range edge case

wp wc generate orders 5 --date-start=2024-06-15 --date-end=2024-06-15

Expected: All orders created with date 2024-06-15 (different times, randomized)

Test 3: Error handling for failed order generation

# Attempt to create orders when no products exist (should skip failed orders gracefully)
wp wc generate orders 5

Expected: Error logged but batch continues; indicates 0 orders generated in the end.

Test 4: Large multi-year batch maintains chronological order

wp wc generate orders 100 --date-start=2023-01-01 --date-end=2024-12-31

Expected: Date range covers the specified period with proper distribution

[Copilot]

Pull Request Overview

This PR implements chronological ordering for batch-generated orders by pre-generating and sorting dates before order creation. When date-start is specified in batch mode, orders created with lower IDs will have earlier or equal dates, ensuring a logical temporal sequence.

• Pre-generates dates for batch operations when date-start is provided
• Refactors date generation logic to use timestamp-based calculations instead of array enumeration
• Adds new generate_batch_dates() method to handle batch date generation with chronological sorting

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[layoutd]

Related to Test 3, I've added another PR because I don't think "Success: 0 orders generated…" is a very accurate message. ("Task failed successfully"): #189