Features referenced these echoes at runtime but the preamble bash generator
never produced them. Added two config reads in generate-preamble-bash.ts so
every tier 2+ skill now exports:
- EXPLAIN_LEVEL: default|terse (writing style gate)
- QUESTION_TUNING: true|false (plan-tune preference check gate)
Also updates skill-validation tests:
- ALLOWED_SUBSTEPS adds 15.0 + 15.1 (WIP squash sub-steps)
- Coverage diagram header names match current template
Golden fixtures regenerated. 6 pre-existing test failures now pass.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>