Surface errors when product MD manifest sync fails( Close #30 )

[kiannidev]

Summary

Fixes #30 — appendProductMdSource() silently returned when the product MD was missing or had malformed frontmatter. Upload and approve flows reported { ok: true } while the canonical MD sources: list stayed stale.

Related Issue

Fixes #30

Change Type

• Bug fix
• Regression tests
• New feature
• UI change
• Security fix

What Changed

• appendProductMdSource() throws when MD file is missing or frontmatter block is invalid
• approveCandidate() and manualUpload() catch MD sync errors and return { ok: false, error: "..." } instead of success
• API routes already map ok: false to HTTP 400
• Added tests/unit/append-product-md.test.ts (3 cases)

Files Changed

File	Change
lib/pipeline/sources.ts	Throw on MD sync failure; propagate from approve/upload
tests/unit/append-product-md.test.ts	Missing MD, bad frontmatter, happy path

Validation

./node_modules/.bin/tsc --noEmit   # pass
npm run build                      # pass
npm test                           # 3 new + existing tests

Test Plan

• Corrupt {slug}.md frontmatter (remove --- delimiters)
• POST upload PDF — expect 400 with Product MD missing valid frontmatter block
• Valid MD — upload succeeds and sources: list updated in frontmatter