fix: stop emitting the envFile deprecation warning on Vite 8

[bravo-kernel]

What

The vite-node server passes envFile: false to createServer. Vite 8 deprecated that option in favour of envDir: false, so every Vite 8 consumer sees this on startup:

The `envFile` option is deprecated, please use `envDir: false` instead.

The key is now picked from the installed Vite major: envDir: false on 8+, envFile: false below.

Why

The warning is emitted from a top-level createServer call inside the plugin, so no consumer config can reach or suppress it — the fix has to be here.

Gated rather than renamed outright because the vite peer range is >=5.0.0. I verified envDir: false is honoured on 7 and 8, but not on 5/6; gating leaves those paths byte-for-byte unchanged.

Also included: a red-CI fix

packages/react-router-devtools/package.json is reformatted ("files": ["dist"] back onto one line). The release bot rewrote it in becd7c9 and the Validation Pipeline did not run on that commit, so biome ci . has been failing on main ever since and every PR inherits the red check. Happy to split it out if you would rather land it separately.

Verified

Same inline config both ways on Vite 8.1.3:

--- envFile: false (current) ---
The `envFile` option is deprecated, please use `envDir: false` instead.
   resolved envDir = false
--- envDir: false (patched) ---
   resolved envDir = false

Identical resolved config, no warning.

biome ci . is clean, test:types passes, test:lib passes.

Note that test-apps/react-router-v8-vite does not reproduce this: inside the workspace the package resolves its own vite@7.2.2 devDependency rather than the app's Vite 8, so the warning only appears in a real consumer install.

Changeset included (patch).

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/react-router-devtools@266

commit: 40a22a2

[bravo-kernel]

I think the docs build failure is unrelated.