Update Python core and agent SDKs for v1.0 release

## Blueprints
- a2ui-core: https://github.com/a2ui-project/a2ui/blob/main/blueprints/modules/a2ui_core.blueprint.md
- a2ui-agent: https://github.com/a2ui-project/a2ui/blob/main/blueprints/modules/a2ui_agent.blueprint.md

## Implementation plan

https://github.com/a2ui-project/a2ui/blob/v1_0/v1_0_implementation_plan.md

## SDKs:

### [a2ui-core](https://pypi.org/project/a2ui-core/)
- [ ] v0.8
- [x] v0.9
- [ ] v1.0

### [a2ui-agent-sdk](https://pypi.org/project/a2ui-agent-sdk/)
- [x] v0.8
- [x] v0.9
- [ ] v1.0

Review the linked blueprints and implementation plan to understand the v1.0 changes. The work involves updating two Python SDKs: a2ui-core and a2ui-agent-sdk. Check the current SDK codebases, likely in separate repositories, and align them with the new specifications. Testing the updated SDKs against the main project will be necessary to confirm compatibility.

Scritto dal modello di indicizzazione a partire dal testo della issue.