App naming and folder slugs

Read this when touching app display names, app folder paths, or any flow that creates/moves an app directory (create, copy, import, rename, blueprint approval, template apply).

• Display names and folder names are separate concepts. All folder derivation and validation lives in src/shared/app_names.ts (renderer + main safe); DB/filesystem collision suffixing lives in src/ipc/utils/app_name_resolution.ts (main only). Do NOT introduce a new slugifier for app folders — template apply once had its own (allocateNewAppPath) and the two competing derivations caused pointless double folder moves (lumen-notes-2 → lumen-notes-2-1) because the allocator counted the app's own folder as a collision.
• slugifyAppPath in src/shared/slugify.ts is only for GitHub repo / Vercel project name defaults (must stay ASCII). App folders use slugifyAppFolderName, which preserves CJK and transliterates accents.
• Windows device names remain reserved when they have an extension (CON.txt). When sanitizing one, insert the safety suffix before the first dot (CON-app.txt); appending it after the extension (CON.txt-app) leaves the reserved base unchanged and fails validation.
• Collision probing must exclude the app being renamed (DB row AND its own on-disk folder), or re-running the same rename inflates suffixes (Todo App 2 → Todo App 3).
• Collision probing is deliberately capped at 1000 candidates to keep a pathological database/filesystem state from blocking a user action indefinitely. Exhausting the cap must surface a DyadErrorKind.Conflict with actionable context; auto-suffixing is not an unbounded guarantee.
• A case-only folder rename (MyApp → myapp) must use fs.rename, never copy-then-delete: on case-insensitive filesystems (macOS/Windows defaults) source and destination are the same physical directory, so the delete step destroys the app.