Clean up overlapping test_cli_validation.py tests

[sunt05]

Summary

test/core/test_cli_validation.py has significant test overlap — 12 tests that could be consolidated to ~5 without losing coverage.

Overlap analysis

• Tests 1, 3, 7 (test_validate_generates_non_empty_report..., test_validate_returns_error_but_writes_output..., test_validate_report_content_quality) all run validate on minimal invalid YAML and check outputs are non-empty/meaningful
• Tests 2, 4 (test_validate_second_run_does_not_truncate..., test_validate_second_run_on_updated_yaml...) both test idempotent re-runs
• Tests 5, 10 (test_second_run_on_user_edited_yaml..., test_validate_with_complex_realistic_yaml) both use the issue_1097 fixture

Suggested consolidation (12 -> 5)

• test_validate_produces_meaningful_output — merges add table to describe hydraulic-process related properties/connections #1, Observed soil moisture can not be used as an input #3, enrich the documentation of major components in the driver subroutine #7
• test_validate_second_run_not_truncated — merges improve coding guidelines #2, Need to expand Benchmark datasets #4
• test_validate_issue_1097_fixture — merges use "urbanised" meteorology for internal physical modules as forcing #5, to update WRF-SUEWS for latest SUEWS kernel #10
• test_validate_windows_paths — merges Urban haze effect #6, Description of "XSMD" in Meteorological Input File #9 (platform-gated)
• test_create_consolidated_report_writes_utf8 — keep as-is (unit test)

Drop candidates

• test_validate_handles_file_permission_scenarios — fragile, platform-dependent, tests OS behaviour more than SUEWS
• test_validate_error_injection_file_write_failure — edge case unlikely to regress