Pages whose filename matches a nav section-id now get a clean pathname
URL (e.g. /timesheet) instead of the hash-based /#pages/timesheet.md.
- _initialPathname captured at IIFE start; handles ?_route= from 404.html
- basePath determined by initBasePath() after nav data loads; subpath
deployments (e.g. /mysite/) handled automatically
- navigateTo() uses replaceState to /slug for section-id pages and falls
back to #hash for everything else
- popstate listener handles browser history if a clean URL was the entry
- resolveSlugToFile() validates that slug is both a section code and has
a pages/{slug}.md entry in navData
- app/404.html added for GitHub Pages SPA routing
https://claude.ai/code/session_01Ai8xRvmrzdhuTKiRQ2fnn9
