docs: add comprehensive client API reference

scripts/api-docgen/generate.ps1

@@ -0,0 +1,10 @@
+$ErrorActionPreference = "Stop"
+$env:GOWORK = "off"
+$env:GOLANG_PROTOBUF_REGISTRATION_CONFLICT = "warn"
+try {
+    go run .
+    if ($LASTEXITCODE -ne 0) { throw "API documentation generation failed" }
+} finally {
+    Remove-Item Env:GOWORK -ErrorAction SilentlyContinue
+    Remove-Item Env:GOLANG_PROTOBUF_REGISTRATION_CONFLICT -ErrorAction SilentlyContinue
+}