Make Projects guides agnostic and add Genie Agents and Jobs

[ivancalvo-dbxs]

Summary

• rewrite Spark Declarative Pipelines, Metric Views, and Dashboards as project-agnostic capability guides
• add Genie Agents with approved source-controlled create or update and Conversation API validation
• add Databricks Jobs with single-task and exact two-task DAG patterns
• remove official documentation URLs and all Reference lines from published content
• validate the complete Projects sequence with Captain against the persistent eval stack

Verification

• npm run build
• npm run typecheck
• site-wide content, syntax, and navigation gates
• Captain cold-start evaluation from Spark Declarative Pipelines through Databricks Jobs

Closes #6
Closes #7