fix(evals): support cross-drive scaffold imports on Windows

[legend91019]

Why

Fixes #458.

On Windows, path.relative() returns an absolute path when the generated badcase directory and the repository helper are on different drives. The scaffold code treated that result as a relative path and prefixed ./, so generated fixtures could not import fixtures.mjs.

This is an eval-only path-resolution fix and does not change BrowserSkill runtime behavior.

What changed

• Resolve the target helper once.
• Preserve the existing relative specifier on the same filesystem root.
• Fall back to pathToFileURL() when the relative result is absolute, which covers cross-drive Windows paths with a valid ESM specifier.

Verification

• On the unmodified d9a78ae baseline with the repository on D: and %TEMP% on C:, the focused test failed (0 passed, 1 failed); the full browser-eval suite reported 22 passed, 1 failed.
• Moving TEMP/TMP to the repository drive made the same unmodified focused test pass (1/1).
• On this branch, Node v22.22.2 focused test: 1 passed, 0 failed.
• Full browser eval: 23 passed, 0 failed; 10 cases and 19 fixture routes validated.
• corepack pnpm exec biome check evals/browser/lib/scaffold-case.mjs
• node --check evals/browser/lib/scaffold-case.mjs
• git diff --check

No screenshot is included because this is a deterministic Node/Windows path-resolution failure with no UI change. The complete Chinese evidence, independent re-verification, and full before/after code are maintained in the local workflow artifact D:\Desktop\open_coding\pr_reviews\Tencent__BrowserSkill__dogfood__windows-cross-drive-eval-scaffold.md and can be provided to maintainers on request.

[NianJiuZst]

LGTM, approving.

The fix is correct. On Windows, path.relative() gives back an absolute path when the two paths are on different drives. Detecting that with isAbsolute() and falling back to pathToFileURL(targetPath).href produces a valid ESM import. When both paths are on the same drive, the generated specifier is the same relative path as before, so cases scaffolded inside the repo don't change.

What I checked:

• Ran the specifier logic with path.win32. A cross-drive pair (C:\…\Temp\… → D:\repo\…\fixtures.mjs) gives an absolute result and file:///D:/repo/evals/browser/lib/fixtures.mjs. A same-drive pair still gives ../../../lib/fixtures.mjs.
• node --test evals/browser/tests/eval.test.mjs on this branch: 15/15 pass (Linux, Node 22).
• Biome is clean on the changed file, and there are no runtime/product changes.

Non-blocking: CI runs the eval tests only on Ubuntu, so the cross-drive path has no automated test. If we want to guard it, moduleSpecifier could take the path functions as a parameter, so a test can call it with path.win32 and a cross-drive pair. Fine as a follow-up.

[legend91019]

你是马哥吗