Feat: graduate multiagent hook events from experimental

[JackYPCOnline]

Description

After serval months, we think it's time we move multiagent hook events out of experimental.

Related Issues

Documentation PR

Type of Change

Bug fix
New feature
Breaking change
Documentation update
Other (please describe):

Testing

How have you tested the change? Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli

• I ran hatch run prepare

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

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[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 4 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...rc/strands/experimental/hooks/multiagent/events.py	0.00%	4 Missing ⚠️

📢 Thoughts on this report? Let us know!

[zastrowm]

Let's make sure to update the docs too. I got asked about multi-agent hooks because it wasn't obvious that the hooks weren't documented with the rest of the hooks.

(right now they're in https://strandsagents.com/latest/documentation/docs/user-guide/concepts/experimental/multi-agent-hooks/)