[pylrn]

Summary

Fixes a copy-paste bug in src/utils/userAgent.ts where Deno runtime detection mistakenly checked process.versions.bun instead of Deno's own version properties:

// Before
if (typeof Deno !== "undefined") {
  if (process.versions.bun && defaultUserAgentString.indexOf("Deno") === -1) {
    defaultUserAgent.runtime_env = { name: "Deno", version: Deno.version.deno };
  }
}

In standard Deno environments without Node compatibility layers, process is undefined and evaluating process.versions.bun could throw a ReferenceError. Even with polyfilled process, process.versions.bun was never truthy, causing Deno runtime identification in the SDK's telemetry header to silently fail.

Changes

• Fix Deno runtime detection to inspect Deno.version?.deno.
• Refactor detector resolution into detectDefaultUserAgent(env?: EnvironmentDetectors) for clean testability and safe environment property access without ReferenceError.
• Add unit tests in tests/unit/utils.test.ts verifying Deno, Bun, and Node environment detection.
• Passes eslint, prettier, and tsc --noEmit cleanly.