Progression line for validator

[dayantur]

After feedback from users, a proposal has emerged to introduce a progression line at the top of the validation report.
The main idea is to clearly indicate at which validation stage the process stopped.

Current report header

# SUEWS Validation Report
# ==================================================
# Mode: Public
# ==================================================

Proposed report header with progression line

• When stopping at pipeline A (Completeness Check):

# SUEWS Validation Report
# ==================================================
# Mode: Public - Validation stage: Completeness Check
# ==================================================

• When stopping at pipeline B (Scientific Validation):

# SUEWS Validation Report
# ==================================================
# Mode: Public - Validation stage: Scientific Validation
# ==================================================

• When stopping at pipeline C (Model Compatibility):

# SUEWS Validation Report
# ==================================================
# Mode: Public - Validation stage: Model Compatibility
# ==================================================

The progression line uses simple, user-facing wording, consistent with the main public documentation (no developer-level details).
Its purpose is to clearly inform users at which validation stage their configuration failed, improving transparency/usability.