Fix daily-rig-game-gen timeout caused by spurious typecheck failures on optional engines

[Copilot]

The Daily Rig Game Generator workflow timed out at 30 minutes (#374). The agent transcript from the failed run shows it stuck for 27+ minutes debugging a --typecheck failure that was unrelated to the generated game code, on every single attempt.

Root cause

rig.ts's defaultAgentFactory lazy-loads the optional anthropic/codex/gemini engines via literal dynamic imports:

const { anthropicEngine } = await import("./engines/anthropic.ts");

TypeScript fully type-checks the module graph reachable from a literal dynamic import specifier, even when that branch is only reached at runtime for a specific engine selection. Since the workflow installs the rig skill standalone (no repo checkout, no npm install), the optional peer deps (@anthropic-ai/sdk, @openai/codex-sdk) are missing, so every --typecheck call failed with:

engines/anthropic.ts(1,23): error TS2307: Cannot find module '@anthropic-ai/sdk' ...
engines/codex.ts(1,23): error TS2307: Cannot find module '@openai/codex-sdk' ...

The agent had no way to fix this (it can't modify the skill's engine files), so it kept regenerating and re-verifying the game program across many attempts until the job was cancelled.

Fix

• skills/rig/rig.ts: route the anthropic/codex/gemini dynamic imports through a new importOptionalEngine(relativePath) helper that passes the specifier via a parameter instead of a literal string:

  async function importOptionalEngine(relativePath: string): Promise<any> {
    return import(relativePath);
  }

  TypeScript cannot statically resolve non-literal dynamic import specifiers, so it treats the result as any and skips transitively type-checking those optional engine modules. Runtime behavior is unchanged — the engines still load correctly when selected.

Tests

• src/launcher.test.ts: added a regression test that simulates a standalone skill install (skill directory copied to a temp dir, node_modules symlinked in minus the optional engine peer deps) and asserts --typecheck still passes.

• Fixes [aw] Daily Rig Game Generator timed out #374