Update agent-development.md with uv run adk tip and warning

[zeroasterisk]

This PR updates the agent development guide to mention uv run adk as an alternative for restricted environments, and adds a warning that instructions to copy a2ui_schema.py are outdated.

[gemini-code-assist]

Code Review

This pull request updates the agent development guide to include a tip for using uv and adds a warning regarding outdated A2UI schema instructions. A review comment suggests improving the warning's clarity by specifying that the entire section is legacy and highlighting the generate_system_prompt() method.

[gemini-code-assist]

The warning is helpful, but the current phrasing might lead users to believe only the file copying step is outdated. Since the entire following section (including imports and prompt construction) uses the legacy approach, it's better to clarify that the whole section is for historical reference. Also, mentioning generate_system_prompt() provides a more direct path to the modern implementation.

Suggested change

	> **WARNING: Outdated Instructions**
	> The instructions below regarding copying `a2ui_schema.py` are outdated. The A2UI schema is now managed by the `a2ui` package provided by the SDK. Please refer to the working samples in `samples/agent/adk/restaurant_finder/agent.py` to see how to use `A2uiSchemaManager` to get the schema and inject it into the prompt.
	For historical reference or if you are using an older version, the previous instructions were:
	Copy the `a2ui_schema.py` from the contact lookup example.
	> **WARNING: Outdated Instructions**
	> The instructions and code examples in the rest of this section regarding `a2ui_schema.py` are outdated. The A2UI schema and prompt injection are now managed by the `A2uiSchemaManager` class in the `a2ui` package. Please refer to the implementation in `samples/agent/adk/restaurant_finder/agent.py` to see how to use `generate_system_prompt()` to automatically include the schema and examples.
	For historical reference, the previous instructions were:
	Copy the `a2ui_schema.py` from the contact lookup example.