fix: Find the nearest .git when a worktree is inside a clone

[kachkaev]

Fixes #8975.

findRepoRoot runs two independent findUp searches and prefers the directory result, so a clone further up wins over a worktree's own .git file:

const foundDir = await vfs.findUp('.git', directory, { type: 'directory' });
const foundFile = await vfs.findUp('.git', directory, { type: 'file' });
const found = foundDir || foundFile;

With useGitignore: true the clone's .gitignore is then applied to the worktree's files, so a worktree kept in a gitignored folder inside its own clone — the .worktrees layout this repository uses itself — has every file treated as ignored and cspell reports Files checked: 0.

This searches once for a .git of either kind, via a predicate, so the nearest one marks the root. That also drops one full walk up the tree.

Note that omitting type is not an alternative: findUpFromUrl defaults it to 'file', so a plain findUp('.git', directory) stops finding normal clones.

The new test builds a clone with a worktree nested inside it under temp/ and checks both roots resolve to themselves. It fails on main with the worktree resolving to the clone.

Verified with the built CLI on a scratch repository, run from a subdirectory of the worktree so that the findRepoRoot(cwd) || cwd fallback in generateGitIgnore cannot mask the result: before, Files checked: 0; after, the misspellings are reported.