Fix false local references from slash-separated prose

[Tomauskasz]

Summary

• Ignore ordinary slash-separated prose such as reads/writes during plain-text reference extraction.
• Preserve explicit extensionless paths such as ./references/guide.
• Preserve extension-bearing paths such as references/guide.md and existing Markdown destinations.

Fixes #450.

Root cause

The plain relative-path pattern accepted a multi-segment token when both the explicit ./ prefix and final file extension were absent. The resolver therefore could not distinguish ordinary prose from an extensionless local path.

The patch requires one explicit path signal for unquoted plain-text references: an explicit ./ prefix or a final extension.

Verification

• tests/nodes/test_security_remediation.py: 70 passed.
• ruff check: passed.
• ruff format --check: passed.
• git diff --check: passed.
• A live local-source scan of n8n-post-change-runtime-proof completed with 100% coverage, zero unresolved references, and analysis_completeness.is_complete: true.

Tradeoff

An unquoted extensionless token such as references/guide is ambiguous with prose. Authors must use ./references/guide, Markdown link syntax, or an extension-bearing path.

AI assistance disclosure

Codex inspected the reference resolver, reproduced the defect, drafted the implementation and tests, and ran the verification commands. I reviewed the root cause, diff, behavior, tradeoff, and final pull-request text.

[Tomauskasz]

End-to-end follow-up:

• All five upstream checks pass.
• Installed the PR as a packaged uv-tool snapshot.
• The target skill's ordinary slash prose produced zero unresolved references.
• Its real Markdown reference still resolved.
• SkillSpector reported LOW/SAFE, 100% coverage, complete analysis, zero ledger exceptions, and exit 0 with --fail-on-incomplete.
• SkillEvaluator then accepted the security report and completed a full four-case paired Tier 3 run.

This confirms the parser change at the installed consumer boundary.