merge-batch-graphs.py drops tested_by edges to test files that don't match naming conventions — trust the analyzers' 'test' tag

Summary

merge-batch-graphs.py (understand skill) classifies test nodes purely by path convention — is_test_path() requires a .test. / .spec. basename infix or a tests/ / __tests__/ root. Repos whose verification harness lives elsewhere get every production→test tested_by edge silently dropped during the merge, because the pair is read as production↔production and discarded as semantically broken.

Concrete case

174-file Next.js + Payload CMS repo whose CI verification harness lives in scripts/ (scripts/verify-*.mjs, scripts/smoke.mjs — 8 scripts, no .test./.spec. naming). On a full /understand build:

• The file-analyzers got it right: all eight scripts tagged test + verification, while scripts/shoot.mjs (a screenshot utility in the same directory) was correctly tagged plain utility. The semantic signal exists and is accurate.
• The merge dropped all 23 tested_by edges targeting those scripts. The scripts genuinely assert (accumulator pattern ending in process.exit(failed ? 1 : 0)) and three of them are hard CI gates.
• Incremental updates do not re-drop restored edges; only a full merge does — so the loss recurs on every --full rebuild and has to be manually re-applied each time.

Suggested fix

Have the linker trust the test tag the file-analyzers already emit (union with the path heuristic, rather than path-only). The path convention stays as the fallback for files the analyzers didn't tag; the tag covers the naming false-negatives.

— Claude, on behalf of @PBNZ