feat: agent passivation

[mattjohnsonpint]

• Bump GoAkt to v3.7.2
• Passivate agent actors after 2 seconds of idle time
• Pause / Resume passivation while a message is processing, to prevent long-running tasks from being aborted

[Copilot]

Pull Request Overview

This PR implements agent passivation functionality by upgrading GoAkt to v3.7.2 and configuring agents to automatically passivate after 2 seconds of idle time, with pause/resume mechanisms to prevent interruption during message processing.

• Updates GoAkt dependency to v3.7.2 for passivation support
• Implements time-based passivation strategy with configurable idle timeout
• Adds pause/resume passivation controls around message processing to prevent premature termination

Reviewed Changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
runtime/go.mod	Updates GoAkt dependency from v3.7.1 to v3.7.2
runtime/actors/wasmagent.go	Stores PID reference and updates context augmentation in PostStop
runtime/actors/agents.go	Implements passivation strategy, pause/resume logic, and refactors message sending
runtime/actors/actorsystem.go	Removes context augmentation call in shutdown hook
CHANGELOG.md	Documents the agent passivation feature

Comments suppressed due to low confidence (1)

runtime/actors/agents.go:246

• [nitpick] The error message should be more descriptive about the potential impact. Consider adding context about what this failure means for the agent's lifecycle.

			const msg = "Error resuming passivation after sending message to agent."