[bug] appendProductMdSource silently skips MD manifest update on missing or malformed frontmatter

[kiannidev]

Duplicate check

Item	Relation
#12 (open)	Not duplicate — scoped source storage layout (line/category vs product dir)
No open issue	Silent MD manifest sync failure on approve/upload

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Summary

After a successful PDF write and sources.yaml update, appendProductMdSource() updates the product MD sources: frontmatter list. If the MD file is missing or lacks valid --- frontmatter, the function returns without error. Callers (manualUpload, approve flow) still return { ok: true }, leaving sources.yaml and DB in sync but the canonical MD manifest stale.

Per CONTRIBUTING, the MD manifest is load-bearing for extraction — silent drift breaks downstream pipeline steps.

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Steps to reproduce

1. Corrupt or delete a product's frontmatter block in {slug}.md (keep file, remove --- delimiters).

2. Upload a PDF:

   curl -sS -X POST http://localhost:3210/api/pipeline/sources/upload \
     -H 'Content-Type: application/json' \
     --data '{ ... valid upload body ... }'

3. Response is success; sources.yaml has the new entry; product MD sources: list is unchanged — no error surfaced.

Silent early returns:

function appendProductMdSource(input: AppendMdSourceInput): void {
  if (!fs.existsSync(input.mdPath)) {
    return;
  }
  const fmMatch = raw.match(/^---\n([\s\S]*?)\n---\n?([\s\S]*)$/);
  if (!fmMatch) return;

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Expected behavior

Missing MD or malformed frontmatter surfaces an error to the caller (4xx/5xx or { ok: false, error: "..." }). Upload/approve should not report full success when MD manifest was not updated.

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Actual behavior

Best-effort no-op; API returns success.

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Suggested fix

1. Change appendProductMdSource to return Result<void> or throw on missing MD / bad frontmatter.
2. Propagate error from manualUpload and approve callers.
3. Add unit test: corrupt frontmatter → caller gets error, sources.yaml optionally rolled back.

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PR scope

~30–50 lines + one test.