Fix path false positives without weakening required-path checks

[LE0-Lin]

Summary

Fix three dead-path false-positive mechanisms found during maintenance of the pinned Next.js source probe:

• distinguish explicit repository/remote slugs from local file references;
• respect immediate closed (if exists) prose conditions without exempting real Markdown links or unrelated paths;
• retain package-relative paths beneath real build/dist/target/.next trees, while keeping instruction discovery unchanged and pruning dependency/admin trees before path-index descent.

Directory aliases are not followed, external/broken links are not indexed, and command/credential checks remain independent. Runtime remains dependency-free on Python 3.10+.

Verification

• 293 unit tests completed, 1 environment-specific skip; all remaining tests passed.
• Demo still reports its original contradiction, dangerous command and missing-path findings (F 56).
• Same complete pinned Next.js archive verified on Linux: all 50,749 entries and supplied context/path facts checked. Both native and research-only root scopes remove the 8 path false-positive signals and retain the context-size warning. No suppressions or source changes.
• English, Simplified and Traditional limitation notes updated together.

Evidence boundary

Next.js is explicitly development-reused, not an independent holdout. Original corpora, protocol, AI response, acquisition failures and frozen tool report remain unchanged. The separate current-code development report identifies its source fingerprints and has no correctness metrics or human reference labels. The score change is not improved instruction quality or measured accuracy.

Volunteer human annotation is deferred without substituting an AI label. No maintainer was contacted and no new model run occurred. Published v0.23.0 artifacts are unchanged; these are unreleased source fixes.