fix: preserve tested_by edges for Swift, Rust, Ruby, and PHP

[ZHCHJ888]

Summary

Extend deterministic test-file classification for Swift, Rust, Ruby, and PHP so valid LLM-emitted tested_by edges are not misclassified as production-to-production relationships and dropped during graph merging.

The change adds language-specific filename and test-directory conventions while preserving the existing JavaScript/TypeScript helper-file behavior.

Linked issue(s)

Closes #646

What changed

• Added test filename conventions for:
  • Swift: *Test.swift, *Tests.swift, and *Spec.swift
  • Rust: test_*.rs and *_test.rs
  • Ruby: test_*.rb, *_test.rb, *_spec.rb, and spec_helper.rb
  • PHP: *Test.php
• Recognize Swift, Rust, and PHP source files below tests/ directories as test files.
• Preserve canonical production-to-test tested_by edges for these languages.
• Allow the existing linker to canonicalize inverted Swift tested_by edges and apply the tested tag to production nodes.
• Added positive classification tests for the new conventions.
• Added negative tests to prevent ordinary production files such as Contest.swift, contest.rs, latest.rb, and Contest.php from being misclassified.
• Added regression coverage for canonical and inverted LLM-emitted edges.
• Added a Swift integration test through the complete merge_and_normalize() path.

Scope

Objective-C .m/.mm classification and reporting extensions without configured test patterns are outside the scope of this focused fix.

This PR focuses on preserving test-coverage relationships for the ecosystems identified in #646.

How I tested this

Test environment:

• Windows
• Node.js 22.23.2
• pnpm 10.6.2, as pinned by the repository

Results:

• merge-batch-graphs.py test suite: 91 passed
• Python CI helper suite: 105 passed, 1 skipped
• Core test suite: 1,012 passed, 1 skipped
• Root test suite: 787 passed, 6 skipped
• Root test files: 38 passed
• pnpm lint: passed
• pnpm build: passed
• git diff --check: passed

Skipped tests

The skipped tests cover POSIX-only filesystem behavior that cannot be reliably tested on Windows, such as case-sensitive filenames, literal backslashes, newlines, and trailing dots. None of them exercise the test-file classification or tested_by edge-preservation logic changed by this PR; all relevant tests ran and passed.

Manual Swift smoke test

Ran merge-batch-graphs.py against a temporary batch containing:

• Sources/App/App.swift
• Tests/AppTests/AppTests.swift
• A canonical tested_by edge from the production file to the test file

Verified that:

• The tested_by edge remained in assembled-graph.json.

• The edge direction remained production → test.

• The production node received the tested tag.

• pnpm lint

• pnpm --filter @understand-anything/core test

• pnpm test

• Manual smoke test (described above)

• pnpm build

Versioning

• Version bumped from 2.9.6 to 2.9.7 in all six manifests listed in CLAUDE.md.