feat: AsyncIterable streaming support for library SDK

[BYK]

Currently the SDK library mode rejects streaming flags (--follow, --refresh) with an error. Commands like log list --follow and dashboard view --refresh yield multiple CommandOutput values over time via async generators — in library mode, these should return an AsyncIterable<T> that consumers iterate with for await...of.

Proposed API

const sdk = createSentrySDK({ token: "..." });

// Streaming: returns AsyncIterable
for await (const log of sdk.log.list({ follow: 5 })) {
  console.log(log);
}

// Non-streaming: returns Promise (unchanged)
const logs = await sdk.log.list({ limit: 10 });

Key challenges

1. Async channel — captureObject needs to push to a queue/channel instead of a single variable. Consumer reads via for await...of.
2. Env lifecycle — setEnv() cleanup cannot run until iteration completes. Needs deferred cleanup tied to AsyncGenerator.return().
3. Telemetry span — withTelemetry uses callback pattern. Streaming needs a handle-based approach where the span stays open during iteration.
4. SIGINT handling — Streaming commands use process.once("SIGINT"). Library mode needs to wire teardown to the AsyncGenerator instead.
5. Codegen overloads — Methods with streaming flags need overloaded signatures: Promise<T> without flag, AsyncIterable<T> with flag.
6. Concurrent env — Global setEnv prevents concurrent streaming. Accept single-stream limitation or refactor to per-invocation env.

Estimate

~450-570 lines across ~12 files. Core channel is simple (~50 lines), integration is the bulk.

Context

PR #565 added the library SDK. Multi-yield accumulation was fixed (array instead of single var), but streaming flags are still blocked.