fix(packages,worker): add VAPI to ProviderName union and drop as any cast

[Harsh23Kashyap]

Fixes #5744.

Summary

vapiProxyRouter calls proxyForwarder(requestWrapper, env, ctx, "VAPI" as any) with an as any cast because "VAPI" is missing from the ProviderName union at packages/cost/providers/mappings.ts:97-135. This PR adds "VAPI" to the union and removes the cast. Runtime behavior is unchanged: VAPI requests still flow through proxyForwarder, and heliconeProviderToModelProviderName returns null for "VAPI" via its existing default: return null; clause (same as today).

This is the type-hygiene follow-up to #5739 (which wired VAPI_PROXY to getVapiProxyRouter).

What changed

• packages/cost/providers/mappings.ts: add "VAPI" to the providersNames array, after "CANOPYWAVE". One line. The ProviderName union now includes "VAPI".
• worker/src/routers/vapiProxyRouter.ts: drop the as any cast on the proxyForwarder call. The literal "VAPI" is now assignable to Provider = ProviderName | "CUSTOM" | ModelProviderName (from worker/src/index.ts:29).
• worker/test/routers/vapiProviderName.spec.ts (new): 6 structural regression tests that read the two source files and assert "VAPI" is in the union, the as any cast is gone, and the router still has the getVapiProxyRouter export and /helicone/test route (positive controls).
• worker/test/routers/vitest.config.mts (new) + worker/vitest.config.mts: register the new test project (mirrors the existing test/alerts node-env pattern).

Why the test is structural

The existing worker/test/ai-gateway vitest config has a pre-existing module-resolution error (Cannot find module '@helicone-package/cost/costCalc') that blocks any test whose import chain touches the worker source from loading. A structural (file-read) check runs in any environment and directly enforces the class of bug this PR fixes (someone re-introducing the as any cast or removing "VAPI" from the union).

Cascades verified

The only switch on ProviderName in the repo is heliconeProviderToModelProviderName in packages/cost/models/provider-helpers.ts:25-86. Its default: return null; clause handles any new union member without an explicit case. The other two switch (provider) statements in packages/cost/ (getUsageProcessor at usage/getUsageProcessor.ts:16 and getThresholdValueFunction at models/calculate-cost.ts:115) operate on ModelProviderName (lowercase), which is a separate type and is not affected.

For "VAPI" the natural mapping in heliconeProviderToModelProviderName is null (no cost calculation, same as the unhandled default). Runtime cost behavior is unchanged.

Verified

• npx tsc --noEmit -p worker/tsconfig.json — clean, no new errors
• npx tsc --noEmit -p packages/tsconfig.json — same 3 pre-existing errors as on upstream/main; none introduced
• cd worker && npx vitest run test/routers/vapiProviderName.spec.ts — 6 passed in 143ms
• Reverting both source changes makes 3 of 6 tests fail, confirming regression detection works
• Full worker vitest: 32 test files, 10 pass (including the new routers project), 22 fail to load with the pre-existing Cannot find module '@helicone-package/cost/costCalc' error; 149 tests run, all pass

Out of scope (deferred to follow-up issues)

• Adding a cost model for VAPI in packages/cost/models/registry.ts and the providers array in packages/cost/providers/mappings.ts:141+. Requires knowing the VAPI upstream URL, the model, and per-token pricing. This PR does not change cost behavior; VAPI requests still report null cost via the existing default: return null; clause.
• Adding a host-routing block in worker/src/index.ts so a vapi.<helicone-domain> host dispatches to WORKER_TYPE: "VAPI_PROXY". Separate product decision.

Risk

Very low. The change is:

• A new string in a const array.
• Removal of an as any cast on a single call site.
• A structural regression test.

Worst case: a switch without a default clause somewhere would now be non-exhaustive. The repo was searched for switches on ProviderName and provider; only the three documented above operate on these types, and all three either operate on a different type (ModelProviderName) or have a default clause.

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Project	Deployment	Actions	Updated (UTC)
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