docs: reorganize nav into grouped sections

Replaces flat 10-item tab bar with 4 grouped sections (Getting Started,
Architecture, Deployment, Project). Adds 3 previously missing pages
(server-contract, deploy-prompt, self-hosted-runners) to the nav.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: baijum

README.md

@@ -8,16 +8,26 @@ Deploy full web applications to your own server directly from GitHub. No custom
 
 Full documentation is available at **[towlion.github.io/platform](https://towlion.github.io/platform)**.
 
-- [Architecture](https://towlion.github.io/platform/architecture/) — platform design, tech stack, diagrams
-- [App Specification](https://towlion.github.io/platform/spec/) — application contract (ports, endpoints, env vars)
+**Getting Started**
 - [Scope](https://towlion.github.io/platform/scope/) — design boundaries and when to use something else
-- [Deployment](https://towlion.github.io/platform/deployment/) — CI/CD pipeline, deploy behavior, migrations
+- [Tutorial](https://towlion.github.io/platform/tutorial/) — step-by-step deployment walkthrough
+
+**Architecture**
+- [Overview](https://towlion.github.io/platform/architecture/) — platform design, tech stack, diagrams
+- [App Specification](https://towlion.github.io/platform/spec/) — application contract (ports, endpoints, env vars)
+- [Server Contract](https://towlion.github.io/platform/server-contract/) — platform-to-workflow interface
+
+**Deployment**
+- [Pipeline](https://towlion.github.io/platform/deployment/) — CI/CD pipeline, deploy behavior, migrations
 - [Self-Hosting](https://towlion.github.io/platform/self-hosting/) — fork model, server requirements, bootstrap
 - [Preview Environments](https://towlion.github.io/platform/preview-environments/) — PR previews, DNS, cleanup
+- [Deploy Prompt](https://towlion.github.io/platform/deploy-prompt/) — reusable deployment session prompt
+- [Self-Hosted Runners](https://towlion.github.io/platform/self-hosted-runners/) — GitHub Actions runner setup
+
+**Project**
 - [Ecosystem](https://towlion.github.io/platform/ecosystem/) — org structure, app template, multi-app hosting
+- [Governance](https://towlion.github.io/platform/governance/) — repository policies and conventions
 - [Roadmap](https://towlion.github.io/platform/roadmap/) — phased development plan
-- [Tutorial](https://towlion.github.io/platform/tutorial/) — step-by-step deployment walkthrough
-- [Server Contract](https://towlion.github.io/platform/server-contract/) — platform-to-workflow interface
 
 ## Project Status
 

mkdocs.yml

@@ -30,17 +30,24 @@ extra_css:
   - stylesheets/custom.css
 
 nav:
-  - Home: index.md
-  - Scope: scope.md
-  - Tutorial: tutorial.md
-  - Architecture: architecture.md
-  - App Specification: spec.md
-  - Deployment: deployment.md
-  - Self-Hosting: self-hosting.md
-  - Preview Environments: preview-environments.md
-  - Ecosystem: ecosystem.md
-  - Governance: governance.md
-  - Roadmap: roadmap.md
+  - Getting Started:
+      - Home: index.md
+      - Scope: scope.md
+      - Tutorial: tutorial.md
+  - Architecture:
+      - Overview: architecture.md
+      - App Specification: spec.md
+      - Server Contract: server-contract.md
+  - Deployment:
+      - Pipeline: deployment.md
+      - Self-Hosting: self-hosting.md
+      - Preview Environments: preview-environments.md
+      - Deploy Prompt: deploy-prompt.md
+      - Self-Hosted Runners: self-hosted-runners.md
+  - Project:
+      - Ecosystem: ecosystem.md
+      - Governance: governance.md
+      - Roadmap: roadmap.md
 
 markdown_extensions:
   - tables