docs: add Architecture, Getting-Started, and split FAQ into categories - Add Architecture-and-Security-Model.md — conceptual "why COI" page covering the threat model, all defense layers, architecture diagram, and what COI does/does not protect against - Add Getting-Started.md — step-by-step first-session walkthrough covering install, coi build, coi shell, resume, parallel sessions, and persistent mode, with links to next steps - Split FAQ.md into three category files: - FAQ-Platform-Comparisons.md (6 questions + comparison table) - FAQ-Security-and-Trust.md (5 questions) - FAQ-Setup-and-Operation.md (9 questions) - Rewrite FAQ.md as a pure index with category table + troubleshooting quick links - Update Home.md: new Getting-Started and Architecture nav section, point new-user callout to Getting-Started, list FAQ category pages

mensfeld committed May 26, 2026