fix: legacy raw-body GraphQL + rababa-to-ML routing (restores the interscript.org demo)

[ronaldtse]

What

Website-driven E2E verification of api.interscript.org found that the live interscript.org demo (React client) has been broken since the Cloudflare cutover:

• It POSTs GraphQL documents as the raw body with a urlencoded content type (accepted by the old Lambda; rejected by Yoga with "Must provide query string"), so the demo's Detect button returns nothing.
• Its Diacritize button calls transliterate with the legacy var-ara-Arab-Arab-rababa system code, which now fails with map_not_found.

Fixes

1. Legacy raw-body GraphQL — the catch-all wraps non-JSON POST bodies as {query} before handing the request to Yoga (server.ts). JSON bodies pass through untouched.
2. Rababa routing — transliterateResolver maps var-ara-Arab-Arab-rababa to the Modal inference service (model ara-diac-1.0, parity-verified ONNX decode). The demo's Diacritize button is now served by our own SOTA Arabic model. ML env is threaded via setMl from the worker env.
3. Red CI repaired — restores the file:vendor/interscript-ts dependency dropped in fbadcbc (CI has been failing typecheck/test/build since then); rewrites gen-models.mjs in pure Node (the embedded python one-liner was committed broken); regenerates the model index to add released heb-diac-1.1 (10 models). dist rebuilt and fully committed.

Tests

• 22 unit tests green (adds: raw-body urlencoded, application/graphql, JSON passthrough, rababa proxied to ML with stubbed fetch).
• E2E suite gains 3 checks (49 total): legacy raw-body transliterate, rababa diacritizes live.
• Verified the Modal service diacritizes مدرسة جميلة -> مَدْرَسَةٌ جَمِيلَةٌ.