docs: restructure navigation and refresh content

[thecaphimself]

Summary

• reorganize Overview and Developer Guide navigation around user paths, products, workflows, and references
• consolidate product documentation, add client-profile pages, and retire redundant routes with redirects
• tighten subtitles and page copy, add developer resources, examples, templates, and troubleshooting guidance
• add pinned local tooling and automated documentation quality checks

Validation

• Mintlify build validation passed
• broken-link check passed
• accessibility check passed with no content issues; primary green meets WCAG AA and reports an optional AAA advisory
• documentation content checks passed for 74 pages and 74 navigation routes
• TypeScript examples passed type checking
• git diff whitespace check passed