Merge https://github.com/google/adk-python/pull/3060
## Description
Fixes#3059
This PR fixes two endpoints in `adk web` that fail when using App objects instead of bare agents.
## Changes
- **Eval execution endpoint** (line ~969): Extract root_agent from App objects before passing to LocalEvalService
- **Graph visualization endpoint** (line ~1308): Extract root_agent from App objects before graph operations
Both endpoints now properly handle both BaseAgent and App objects by checking the type and extracting `.root_agent` when needed.
## Testing Plan
### Manual E2E Testing with ADK Web
Tested with an App object that includes context caching:
```python
from google.adk.apps import App
from google.adk.agents import LlmAgent
root_agent = LlmAgent(name="MyAgent", model="gemini-1.5-pro-002")
app = App(
name="my_agent",
root_agent=root_agent,
context_cache_config=ContextCacheConfig(...)
)
```
**Before fix:**
- Graph visualization failed (tried to call agent methods on App object)
- Eval execution failed (LocalEvalService received App instead of agent)
**After fix:**
- Graph visualization works correctly
- Eval execution works correctly
- Both endpoints properly extract root_agent from App objects
## Checklist
- [x] Code follows project style (autoformat.sh passed)
- [x] Changes are focused and minimal
- [x] Issue #3059 created and referenced
- [x] Manual E2E testing completed
COPYBARA_INTEGRATE_REVIEW=https://github.com/google/adk-python/pull/3060 from ejfn:ejfn/bugfix-app-object-endpoints 01c30191bfd9487a8c8463ccf24b297cb9a4ce37
PiperOrigin-RevId: 821746910
