fix: move once.Do(close(allDone)) from Reboot() to Release()

[Copilot]

1. Are you opening this pull request for bug-fixs, optimizations or new feature?

Bug fix — data race between Reboot() and running workers on once.Do(func() { close(p.allDone) }).

2. Please describe how these code changes achieve your intention.

The once.Do(close(allDone)) in Reboot() existed solely to handle the edge case where a pool with zero workers would block on <-p.allDone indefinitely. But placing it in Reboot() creates a race with workers that are still shutting down and calling the same once.Do in their defer.

The fundamental fix: Release() is the state transition that marks the pool CLOSED, so it's the correct place to close allDone when no workers are running. If workers are still active, the last one to exit closes it in its defer as before. sync.Once guarantees exactly-one-execution regardless of ordering.

• Move if p.Running() == 0 { p.once.Do(func() { close(p.allDone) }) } to end of Release()
• Remove the same check from Reboot() — it now simply does <-p.allDone
• Remove the redundant check from ReleaseContext() (already handled by Release())
• Remove workerWg sync.WaitGroup — no longer needed since there's no race to coordinate in Reboot()

3. Please link to the relevant issues (if any).

4. Which documentation changes (if any) need to be made/updated because of this PR?

None.

4. Checklist

• I have squashed all insignificant commits.
• I have commented my code for explaining package types, values, functions, and non-obvious lines.
• I have written unit tests and verified that all tests passes (if needed).
• I have documented feature info on the README (only when this PR is adding a new feature).
• (optional) I am willing to help maintain this change if there are issues with it later.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.11%. Comparing base (0191bb5) to head (a04a4dc).

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #397      +/-   ##
==========================================
+ Coverage   94.26%   95.11%   +0.84%     
==========================================
  Files          14       14              
  Lines         802      798       -4     
==========================================
+ Hits          756      759       +3     
+ Misses         31       26       -5     
+ Partials       15       13       -2     

Flag	Coverage Δ
unittests	95.11% <100.00%> (+0.84%)	⬆️

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[Copilot]

Pull request overview

This PR addresses a concurrency issue around pool shutdown/reboot by changing when allDone is closed: instead of conditionally closing it in Reboot() / ReleaseContext(), it now closes in Release() when there are no running workers, with the intent to avoid a race with worker shutdown.

Changes:

• Move the Running()==0 + once.Do(close(allDone)) fast-path from Reboot() into Release().
• Remove the redundant allDone close fast-path from ReleaseContext().
• Simplify Reboot() to always wait on <-p.allDone, relying on Release() or the last worker to close it.

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