fix: opening individual modules in monorepo

[arnold095]

This PR fixes two related regressions in the IntelliJ Biome plugin’s configuration resolution logic (see issue #201):

Restore upward search to the project root

Problem (v1.7.2): findNearestFile no longer included the specified root directory in its upward traversal, causing the LSP server not to start when opening only a submodule.

Solution: Adjusted the loop in findNearestFile so that it continues searching until it reaches the root (if provided) or the filesystem root, and includes root in the search.

Allow submodule configs in findNearestBiomeConfig

Problem (v1.9.0): After PR #196, findNearestBiomeConfig filtered out any biome.json that wasn’t marked as a “root” config, even when opening a single submodule, so local configs were ignored.

Solution: Updated the predicate to skip the isRootConfig() check whenever a root directory is supplied—i.e. when operating in submodule mode, the first biome.json found is accepted regardless of its root flag or extends setting. In full-monorepo mode (root == null), the original isRootConfig() requirement remains.

[siketyan]

This isn't correct, root is always NOT null unless we can't find the project root. This changes breaks the new-style monorepo support and launches a Biome instance for each package. I think we should use the child config only when we have searched to the project root and no root config was found.