Add bounded retry policy for transient Drand and Soroban keeper opera…

[Anieblin]

Closes #4

---

…tions

[drips-wave]

@Anieblin Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits

[karagozemin]

Thanks for the PR. I tested the current head (7397ac0) in a clean merge simulation against current main.

Commands run:

• pnpm tlock:test
• pnpm keeper:test
• pnpm --filter @sub-rosa/tlock typecheck
• pnpm --filter @sub-rosa/keeper typecheck

This cannot be merged yet because the keeper package is currently broken after the merge.

Observed failures:

• keeper tests fail at runtime because @sub-rosa/tlock does not export fetchRoundSignatureWithRetry.
• keeper typecheck also reports missing exports for fetchRoundSignatureWithRetry, withRetry, retryPolicyFromEnv, RetryPolicy, and defaultRetryPolicy.
• keeper.ts also has implicit any logger parameters after the failed imports.

Additional acceptance gaps to fix while updating:

• packages/tlock/src/retry.test.ts is not wired into the @sub-rosa/tlock test script, so pnpm tlock:test does not run the new retry tests.
• Watch-mode retry environment configuration should be documented outside source comments, for example in .env.example and/or docs/DEPLOY.md.
• Please add a real keeper test for retrying transient Drand fetch failures. The current Drand retry test only asserts policy shape; it does not exercise keepRound or Drand retry behavior.

After those are fixed, please make sure these pass deterministically:

• pnpm tlock:test
• pnpm keeper:test
• pnpm --filter @sub-rosa/tlock typecheck
• pnpm --filter @sub-rosa/keeper typecheck