docs(locadex): explain file scoping and commands for monorepos - #375

Summary

• Adds a "How file selection is scoped" section: setting App Root Directory scopes which files Locadex reads and translates to that directory, so a shared packages/ui or a sibling app is left alone. Points at the Select Files step in Run Agent for narrowing a single run.
• Adds a monorepo layout example so it is clear what to put in App Root Directory.
• Expands "Configure commands" with a cd example and workspace-filter commands for npm, yarn, bun, and pnpm.
• Config reference: the App Root Directory bullet now mentions the file-scoping behavior and links to the guide.

Testing

• unsafe-HTML and link validators pass; pnpm build:content builds all 428 pages with TypeScript passing.

Notes

• Everything is Dashboard-focused and verified against the locadex source in gt-cloud. No internal CLI flags or config files are documented.