fix(#769): drive retry-backoff tests with a simulated actor clock

[zgeoff]

Description

Closes #769

The submitter retry tests ran on real 5–20ms backoff timers, so CI load could slide an extra retry attempt (or one fewer) across an assertion window — the held-count test flaked both directions on GitHub runners. Retry timing is now driven by an injected xstate clock, so a backoff attempt fires only on an explicit clock.increment.

• createCheckpointSubmitter takes a test-only clock option, forwarded to the parent actor; spawned per-activity children inherit it through the actor system.
• The clock option is only forwarded when present — an options object carrying clock: undefined clobbers xstate's default system clock.
• Both submission suites use SimulatedClock; the test-only retryTimings override is gone, tests advance past the production timings instead.
• Real-time sleeps proving no-further-attempts became clock increments past the backoff cap.
• Clock joins the readonly-parameter-types allow list: a two-method behaviour handle with no readonly form.

Testing

• bun run typecheck passes
• bun run test passes
• bun run lint passes
• New tests added for new functionality

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📝 Walkthrough

Walkthrough

The submitter now accepts an optional XState clock, and retry-related tests use SimulatedClock advancement with fixed backoff constants instead of per-test real-time timing overrides.

Changes

Checkpoint retry timing

Layer / File(s)	Summary
Submitter clock injection libs/game/idle-client/src/submission/create-checkpoint-submitter.ts, .oxlintrc.json	The submitter accepts an optional actor clock, conditionally passes it to XState, and allowlists the Clock type for readonly-parameter linting.
Activity machine simulated-clock tests libs/game/idle-client/src/submission/checkpoint-activity-machine.test.ts	Activity machine tests use a simulated clock, fixed retry timing input, explicit backoff advancement, and exact retry/state assertions.
Submitter retry-flow tests libs/game/idle-client/src/submission/create-checkpoint-submitter.test.ts	Submitter retry, loop replacement, held checkpoint, failure, and shutdown tests use simulated backoff advancement instead of retryTimings overrides and real-time waits.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Possibly related PRs

• zgeoff/vers#580: Related checkpoint submitter retry/backoff and flushHeld changes.
• zgeoff/vers#599: Also modifies checkpoint submitter options and callback wiring.
• zgeoff/vers#743: Related XState checkpoint submitter and retry timer behavior.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: using a simulated actor clock for retry-backoff tests.
Description check	✅ Passed	The description is directly related to the PR and accurately describes the simulated-clock retry test changes.
Linked Issues check	✅ Passed	The PR addresses #769 by making retry-loop tests deterministic with explicit simulated-clock advancement.
Out of Scope Changes check	✅ Passed	The changes stay focused on the retry-test flake fix and supporting clock plumbing, with no clear unrelated additions.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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• Create PR with unit tests
• Commit unit tests in branch fix/769-deterministic-retry-clock

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Actionable comments posted: 1

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Verify each finding against current code. Fix only still-valid issues, skip the
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Inline comments:
In `@libs/game/idle-client/src/submission/checkpoint-activity-machine.test.ts`:
- Line 47: Update the direct-machine test fixture’s retryTimings to reference
the imported production retry timing constants instead of duplicating literal
maxTimeout and minTimeout values. Keep the test aligned with the production
configuration and preserve the existing retry behavior.

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📥 Commits

Reviewing files that changed from the base of the PR and between 9752a5f and c0abf20.

📒 Files selected for processing (4)

• .oxlintrc.json
• libs/game/idle-client/src/submission/checkpoint-activity-machine.test.ts
• libs/game/idle-client/src/submission/create-checkpoint-submitter.test.ts
• libs/game/idle-client/src/submission/create-checkpoint-submitter.ts