feat: publish LAB 02 spatial EDA

[EHDataAI]

Summary

• publishes LAB 02: Spatial Exploratory Data Analysis;
• demonstrates why sampling density must be distinguished from underlying spatial signal;
• adds a recruiter-facing executed notebook and standalone Python walkthrough;
• adds reusable spatial-analysis utilities and automated tests;
• publishes persisted synthetic Monte Carlo results for resolution sensitivity;
• adds documented Natural Earth geographic context and provenance;
• updates the public portfolio roadmap, repository structure, and validation metrics;
• keeps internal experiment-generation and notebook-orchestration tooling outside the public portfolio.

Validation

• 24 automated tests passed;
• standalone LAB 02 analysis executed successfully;
• notebook schema validation passed;
• 31 notebook cells;
• 13 / 13 code cells executed in the persisted notebook;
• 0 persisted notebook error outputs;
• 6 embedded PNG figures;
• publication leakage scan passed with 0 forbidden references;
• no tracked cache or bytecode files;
• pre-commit passed;
• Gitleaks passed;
• private-key detection passed;
• large-file check passed;
• git diff --check passed;
• commit signature verified by GitHub.