Implement typed async generators

[ctate]

Summary

• implement typed async generator declarations, generic instantiations, function expressions, object methods, public class methods, and private methods
• add the queued next / return / throw request protocol with Node-compatible eager starts, promise settlement ordering, exception rejection, finally behavior, and reference-counted ownership
• lower for await over typed async generators and support the node:timers/promises setInterval(delay, value) async iterator
• emit the protocol through both C and LLVM, including WASI switched-coroutine support, and regenerate the compatibility/docs artifacts

Closes #170.

Validation

• pnpm -r build
• changed-file ESLint with --quiet
• pnpm node-compat:check
• docs NEXT_DIST_DIR=.next-check pnpm check
• TypeScript 7 adapter/order suites, with the 5.9.3 order baseline re-recorded for new corpus fixtures
• focused C and LLVM differential runs in plain and ASan/RC-audit modes
• wasm32-wasi runs for the async-generator protocol and timers/promises interval fixtures
• rebuilt and verified @scriptc/runtime-darwin-arm64
• pnpm test:sandbox: all plain and sanitized Linux Sandbox shards plus local Darwin/cross-target contracts passed; cold managed-image gate completed in 12.2 minutes

Deliberate boundaries

Async yield*, arbitrary structural async-iterator objects, and timers/promises.setInterval AbortSignal options remain explicitly fenced. The implemented delegation spelling is an explicit for await loop. Library-mode generator exports retain their existing refusal.

Coordination

This touches the scheduler/runtime, IR, and emitter files also modified by #288. The features are orthogonal, but whichever PR lands second will need a focused rebase around those shared seams.

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Project	Deployment	Actions	Updated
scriptc	Ready	Preview, v0	Sep 14, 2026 5:34am UTC