feat: simplify setup link API and TypeScript SDK (#556)

## Summary

- make setup-link targeting explicit while preserving the existing
setup-link request fields
- add idempotent setup-link creation and direct entry points for gateway
providers
- simplify TypeScript SDK request inputs so operation bodies are passed
directly and workspace can come from the API key
- capture bounded provider error responses for internal diagnostics
while keeping gateway responses sanitized
- regenerate the Platform TypeScript SDK from the updated OpenAPI
contract

## Validation

- AI Gateway unit tests pass (90 tests)
- TypeScript SDK was regenerated from the source OpenAPI schema
- real-provider failure path verified: the upstream 400 body is captured
internally while the caller receives the sanitized gateway error

## Merge order

Merge this PR before the corresponding Platform PR, which consumes the
new AI usage diagnostic fields.

Author: alongubkin

client-sdks/platform/openapi.json

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+repo_root="$(cd "$(dirname "${BASH_SOURCE[0]}")/../../.." && pwd)"
+sdk_dir="$repo_root/client-sdks/platform/typescript"
+schema="$repo_root/client-sdks/platform/openapi.json"
+overlay="$repo_root/client-sdks/platform/speakeasy-overlay.yaml"
+temp_dir="$(mktemp -d)"
+
+cleanup() {
+  rm -rf "$temp_dir"
+}
+trap cleanup EXIT
+
+speakeasy overlay apply \
+  --strict \
+  --schema "$schema" \
+  --overlay "$overlay" \
+  --out "$temp_dir/openapi.json"
+
+speakeasy generate sdk \
+  --lang typescript \
+  --schema "$temp_dir/openapi.json" \
+  --out "$sdk_dir"
+
+NODE_OPTIONS=--max-old-space-size=12288 pnpm -C "$sdk_dir" build

client-sdks/platform/rust/openapi-3.0.json

@@ -0,0 +1,20 @@
+overlay: 1.0.0
+info:
+  title: Platform TypeScript SDK ergonomics
+  version: 1.0.0
+actions:
+  - target: "$"
+    update:
+      x-speakeasy-globals:
+        parameters:
+          - name: workspace
+            in: query
+            description: Workspace name. Platform API keys already select a workspace; other authentication methods can configure it once on the SDK client.
+            required: false
+            schema:
+              type: string
+              minLength: 4
+              maxLength: 100
+              pattern: "^(?!ws[-_])[a-z0-9](-?[a-z0-9])*$"
+            example: my-workspace
+            x-speakeasy-globals-hidden: true

client-sdks/platform/rust/openapi.json

@@ -33,7 +33,7 @@ generation:
     skipResponseBodyAssertions: false
   versioningStrategy: manual
 typescript:
-  version: 3.3.18
+  version: 3.4.1
   acceptHeaderEnum: true
   additionalDependencies:
     dependencies: {}