feat: enable always online bot users

[slack-samples]

Type of change

• New feature

Summary

Enables features.bot_user.always_online for this sample app manifest.

Updated manifest files:

• claude-agent-sdk/manifest.json
• openai-agents-sdk/manifest.json
• pydantic-ai/manifest.json

Requirements

• I have ensured the changes I am contributing align with existing patterns and have tested and linted my code
• I've read and agree to the Code of Conduct

Testing

• Parsed each changed manifest.json as valid JSON.
• Verified each changed manifest has features.bot_user.always_online === true.

Reviewers

Please verify the sample can still be created with Slack CLI using this branch:

$ slack create -t slack-samples/bolt-python-support-agent --subdir claude-agent-sdk --branch claw/always-online-manifests-2026-05-27
$ slack create -t slack-samples/bolt-python-support-agent --subdir openai-agents-sdk --branch claw/always-online-manifests-2026-05-27
$ slack create -t slack-samples/bolt-python-support-agent --subdir pydantic-ai --branch claw/always-online-manifests-2026-05-27

[zimeg]

LGTM - enabling always_online for bot users