Ship TypeScript declarations with foundry-local-sdk (#666)

`package.json` advertised `"types": "dist/index.d.ts"`, but the build
never emitted declarations — consumers importing `foundry-local-sdk`
from TypeScript got no IntelliSense or type checking.

### Changes

- **`sdk/js/tsconfig.build.json`** — enable `declaration: true` and
`sourceMap: true`. Scoped to the build tsconfig so tests/examples are
unaffected. `declarationMap` is intentionally omitted to keep `src/` out
of the tarball.
- **`sdk/js/README.md`** — add a short "TypeScript support" section so
the bundled typings are discoverable.

No changes needed in `package.json` or `script/pack.cjs`: `dist/` is
already in `files`, so the 16 emitted `.d.ts` files (`index`, `catalog`,
`foundryLocalManager`, `configuration`, `imodel`, `types`, `openai/*`,
`detail/*`) flow into the tarball automatically. The
`foundry-local-sdk-winml` variant continues to inherit types
transitively via its `foundry-local-sdk` dependency.

```jsonc
// sdk/js/tsconfig.build.json
"compilerOptions": {
  "rootDir": "./src",
  "outDir": "./dist",
  "declaration": true,
  "sourceMap": true
}
```

`@internal`-tagged exports (`Model`, `ModelVariant`, `CoreInterop`,
`Configuration`) are left in the emitted declarations to keep the public
surface unchanged from what the `.js` already exposes; `stripInternal`
can be layered on as a follow-up if tightening the advertised API is
desired.

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: baijumeswani <12852605+baijumeswani@users.noreply.github.com>

Author: Copilot

sdk/js/README.md

@@ -21,6 +21,12 @@ The Foundry Local JS SDK provides a JavaScript/TypeScript interface for running
 npm install foundry-local-sdk
 ```
 
+## TypeScript support
+
+The package is authored in TypeScript and ships with bundled type declarations (`.d.ts` files) alongside the compiled JavaScript. No `@types/foundry-local-sdk` package or manual ambient declarations are needed.
+
+Importing from `foundry-local-sdk` in a TypeScript project gives you full type information and IntelliSense for every public API, including `FoundryLocalManager`, `Catalog`, `ChatClient`, `AudioClient`, `EmbeddingClient`, `ResponsesClient`, `LiveAudioTranscriptionSession`, and all of their associated option and response types.
+
 ## WinML: Automatic Hardware Acceleration (Windows)
 
 On Windows, install the WinML package to enable automatic execution provider management. The SDK will automatically discover, download, and register hardware-specific execution providers (e.g., Qualcomm QNN for NPU acceleration) via the Windows App Runtime — no manual driver or EP setup required.

sdk/js/tsconfig.build.json

@@ -2,7 +2,9 @@
   "extends": "./tsconfig.json",
   "compilerOptions": {
     "rootDir": "./src",
-    "outDir": "./dist"
+    "outDir": "./dist",
+    "declaration": true,
+    "sourceMap": true
   },
   "include": ["src/**/*"],
   "exclude": ["node_modules", "test", "examples"]