fix(download): classify relative media URLs instead of throwing

[MaxFreedomPollard]

Description

detectContentType() builds the extension it classifies on from new URL(url).pathname (src/download/index.ts:92). new URL() rejects a relative path like /media/photo.jpg and a protocol-relative one like //cdn.example.com/clip.mp4, so the call throws TypeError: Invalid URL on exactly the values adapters produce when a site's JSON returns unqualified media paths.

The pipeline download step calls it at src/pipeline/steps/download.ts:238, which sits above the per-item try block. The TypeError escapes the mapConcurrent worker and rejects the whole step, so one bad row kills every other download in the batch and the step's own { status: 'failed' } result for that row is never produced. requiresYtdlp() sitting right next to it already tolerates unparseable URLs (there is a test for that); detectContentType() did not, even though the test above it calls both on the same URLs.

Extension sniffing now goes through a small urlPathForExtension() helper that falls back to trimming the query and hash by hand when new URL() rejects the input. /media/photo.jpg classifies as image and //cdn.example.com/clip.mp4 as video, and a genuinely unusable URL now fails as one item (httpDownload reports it) instead of as the batch.

Related issue:

Type of Change

• 🐛 Bug fix
• ✨ New feature
• 🌐 New site adapter
• 📝 Documentation
• ♻️ Refactor
• 🔧 CI / build / tooling

Checklist

• I ran the checks relevant to this PR
• I updated tests or docs if needed
• I included output or screenshots when useful

Screenshots / Output

Three regression tests were added. On main without the source change all three fail with TypeError: Invalid URL raised at src/download/index.ts:92, the pipeline one through mapConcurrent at src/utils.ts:31:

FAIL |unit| src/download/index.test.ts > returns false for an unparseable URL instead of throwing
FAIL |unit| src/download/index.test.ts > classifies relative and protocol-relative media URLs by extension
FAIL |unit| src/pipeline/steps/download.test.ts > keeps downloading the rest of a batch when one item has an unparseable URL
Tests  3 failed | 12 passed (15)

With the fix:

npx vitest run --project unit src/download/index.test.ts src/pipeline/steps/download.test.ts
Test Files  2 passed (2)
Tests  15 passed (15)

npx tsc --noEmit
(clean)

npm test
Test Files  631 passed (631)
Tests  7318 passed | 1 skipped (7319)

npm run check:silent-column-drop
Silent-column-drop gate: current=94, baseline=94, new=0, resolved=0

npm run check:typed-error-lint
Typed-error lint gate: current=130, baseline=130, new=0, resolved=0

npm run build && git diff --exit-code -- cli-manifest.json
(no drift)