feat(rmi): add curated agentic skills suite for Roads Management Insights

[n0531m]

Description

This PR introduces a curated suite of Agentic Skills for Roads Management Insights (RMI) under roads_management_insights/.agents/skills/.

These skills provide AI coding assistants (Jetski, Antigravity, Gemini CLI, Cursor, Claude Code) with domain runbooks, pre-validated SQL queries, API documentation, and operational procedures for RMI development and analytics.

Included Skills (12 Total)

• api-analyticshub: BigQuery Analytics Hub exchanges, shared listings, and linked datasets.
• api-roadsselection: Roads Selection API v1 route definition (up to 25 waypoints) and management.
• api-discovery: Google API Discovery Service exploration and doc fetching.
• bigquery-geospatial: BigQuery GIS capabilities (ST_* functions, spatial clustering/indexing).
• bigquery-practices: Foundational SQL best practices, partition pruning, and performance.
• rmi-routesetting: Route selection strategies and path transformation logic.
• rmi-sql: Production and analytical SQL templates for trip durations, SRIs, and bottleneck metrics.
• rmi-data-foundation-bigquery: Foundation schemas (routes_status, historical_travel_time).
• rmi-data-realtime-bigquery: Near real-time recent_roads_data table analytics.
• rmi-data-realtime-pubsub: Telemetry ingestion stream and backfill patterns.
• rmi-sampledatasets: Regional sample datasets (Boston snapshot) validation guidelines.
• rmi-dataviz: Geospatial visualization guidelines (Deck.gl and Google Maps).

Package & Consumption Support

• Zero-Config Workspace Discovery: Automatically discovered via hierarchical tree traversal when working in roads_management_insights/.
• Universal Agent CLI (skills.sh): Fully compatible with npx skills add https://github.com/googlemaps-samples/insights-samples/tree/main/roads_management_insights.
• Clean Lifecycle & Traceability: Isolated to .agents/skills/ with .bundle-manifest.json SHA256 verification and catalog documentation.