feat: discover default Remix and React Router file routes

[bompus]

Behavior

Discover default Remix file routes and React Router configurations that register an imported, option-free flatRoutes() call. Pages bind their exact default components; dot nesting, index/pathless segments, parameters, optional segments, splats and bracket escapes preserve route paths. Explicit configuration routes can coexist with file routes.

Configuration-only full/scoped sync, including reopening an index, adds or removes existing page routes when the convention changes. Resource-only modules and direct Outlet-only layouts are excluded. Custom roots/configuration, folder index fallback and Markdown/MDX are outside this change.

Validation

• Build and 102 focused WASM/control tests pass, including fresh compiled parse/resolver workers.
• Full native suite: 4,415 passed, 46 skipped.
• Independent correctness and complexity review is clear.

Stacked on codex/tanstack-start-routes (PR #4).