fix: adjust cluster sync settings and delays

[mattjohnsonpint]

• Adjust cluster sync default settings based on results of further testing
• Add delays where needed to allow time for peer sync
• Some refactoring and comments added

[Copilot]

Pull Request Overview

This PR refines cluster synchronization behavior by centralizing configuration into helper functions, introducing delays to ensure state consistency, and cleaning up log noise.

• Refactor cluster default settings into dedicated functions (hosts, timeouts, intervals, partition count).
• Add waitForClusterSync calls to coordinate actor spawning across nodes.
• Filter expected shutdown messages in actor logger and bump dependencies.

Reviewed Changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
runtime/go.mod	Bump goakt dependency to v3.6.6 and update version checksum
runtime/actors/cluster.go	Extract cluster settings into helper functions; adjust defaults
runtime/actors/agents.go	Add waitForClusterSync after spawning a new agent actor
runtime/actors/actorsystem.go	Invoke waitForClusterSync on startup; refactor agent restoration
runtime/actors/actorlogger.go	Suppress expected semaphore cancellation logs
CHANGELOG.md	Document new alpha version with sync improvements

Comments suppressed due to low confidence (1)

runtime/actors/cluster.go:154

• [nitpick] The new helper functions (remotingHost, partitionCount, readTimeout, etc.) are not covered by tests. Adding unit tests for these will ensure environment-variable overrides work as expected.

func remotingHost() string {