Add unit tests for checklist-runner module

[nikolasdehor]

Problem

The checklist-runner module (.aios-core/core/orchestration/checklist-runner.js) has no unit test coverage. This module handles validation checklist execution including YAML/markdown parsing, file validation, and summary generation.

Solution

Add comprehensive unit tests covering all public methods and edge cases.

Test Details

Area	Tests	Key Scenarios
constructor	1	Path initialization
loadChecklist	4	File loading, .md extension handling, missing files
parseChecklistItems	5	Markdown checkboxes, YAML blocks, invalid YAML, deduplication
normalizeItem	4	String/object normalization, blocker flags, validation keys
evaluateItem	4	Manual items, validation execution, error handling, custom messages
executeValidation	11	file exists, directory exists, not empty, contains, min size, arrays
run	3	Missing checklist, pass/fail, blocker items
getSummary	2	Missing checklist, category summary
Total	37

[nikolasdehor]

Covered by consolidated PR #426