bug: build_context emits OS-native (backslash) component paths on Windows — non-portable SARIF + Windows test failures #86

Summary

build_context emits OS-native path separators for relative component paths. On Windows this produces backslashes (e.g. references\guide.md), where every other consumer expects forward slashes.

In src/skillspector/nodes/build_context.py, the relative path is built with str(item.relative_to(skill_dir)), which yields references\guide.md on Windows.

Why it matters

These relative paths are used as:

• keys in components / file_cache / component_metadata, and
• SARIF physicalLocation URIs, which are meant to be portable, forward-slash, URI-style paths.

So on Windows the generated SARIF report contains non-portable backslash locations, and any integrator (or test) that keys findings by forward-slash paths silently mismatches. It also makes the unit/integration suite fail on Windows (11 tests in test_build_context.py and the semantic-analyzer fixtures), which raises the barrier for contributors developing on Windows.

Fix

Use Path.as_posix() so component paths are forward-slash on every OS, in build_context and the handful of test helpers that mirror the same relative_to logic. One-line, behavior-preserving on Linux/macOS (where str() already produces forward slashes).

I have the fix ready and will open a small PR referencing this issue.