feat(rmi): synchronize rmi-sql suite for July 2026 dataset and harmonize attribute schemas

[n0531m]

Summary

This PR synchronizes the Roads Management Insights (RMI) Agentic Skills Suite to align with the refreshed July 2026 Boston sample dataset (rmi_sample_data___boston).

Key Enhancements & Refinements:

1. July 2026 Date Boundary Synchronization:
   • Updated all 36 analytical SQL query files across the 6 personas (bigquery_admin, data_engineer, data_scientist, rmi_planner, traffic_operations_manager, urban_planner) to target July 2026 (2026-07-01 through 2026-07-30).
   • Aligned all 6 interactive Jupyter Notebooks and SKILL.md reference queries.
2. Robust Attribute Extraction Harmonization:
   • Added standard COALESCE fallbacks for custom route attributes (route_length_meters / route_length, priority / tier).
   • Ensures 100% resilience across dataset variations without schema mismatches.
3. Validation & Testing:
   • Dry-Run Validation: 36 / 36 queries passed schema resolution and syntax checks.
   • Live BigQuery Execution: 36 / 36 queries succeeded against live sample data (34 returning active data, 2 cleanly confirming healthy operational status).
   • Zero Environment Leakage: Cleaned all personal/environment identifiers and confirmed portable relative links.
4. Agent Isolation:
   • Published strictly the 15 production skills suite (skills/). Local agents are excluded from this release.

CC: @googlemaps-samples