fix: do not bind ":branch" to "new" from onboarding URLs

[jeffal]

Description

Fixes #3976.

/bundles/new and /tests/new are onboarding URLs, not branch URLs. The repo-page route in src/App.tsx was capturing new as :branch and propagating it through useNavLinks into sibling tab links, breaking branch filtering.

Notable Changes

• Match the literal onboarding paths first so :branch stays undefined on those URLs.
• Add matchPath tests over the route patterns to cover both onboarding and branch URLs.

---

Note

Low Risk
Small router ordering change in App.tsx with regression tests; no auth, data, or API surface changes.

Overview
Fixes repo-page routing so bundle and test onboarding URLs (/bundles/new, /tests/new) are not parsed as branch-scoped paths.

The shared REPO_PAGE_ROUTE_PATHS list now registers those literal paths before the bundles/:branch and tests/:branch patterns, so :branch stays unset on onboarding and real branch segments still match. RepoPage uses this exported list instead of an inline path array. matchPath tests lock in onboarding vs branch behavior.

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[jeffal]

Hi Codecov folks 👋 may I have a review? cc @calvin-codecov @drazisil-codecov