to_a2a() overrides the google_adk logger level set by the application #7462

🔴 Required Information

Describe the Bug:
to_a2a() calls logging.getLogger("google_adk").setLevel(logging.INFO) every time it runs, so whatever level the application already set on the google_adk logger gets replaced with INFO.

This shows up when serving the app with something like uvicorn my_agent:a2a_app --log-config logging.json where the config sets google_adk to DEBUG. Uvicorn applies the log config before importing the module, then to_a2a() runs at import time and puts the level back to INFO, so the ADK debug logs never appear. It works the other way too: if you turn google_adk down to WARNING to quiet it, INFO messages come back after calling to_a2a().

The comment above that line says it's there so logs are visible when running under uvicorn directly, but it doesn't really achieve that. Uvicorn's default logging config doesn't put a handler on the root logger, so ADK's INFO records aren't printed with or without the line.

Steps to Reproduce:

1. Install google-adk
2. Run the snippet below
3. It prints INFO instead of DEBUG

Expected Behavior:
to_a2a() should leave the logger level alone. Logging configuration belongs to the application.

Observed Behavior:
The google_adk logger is always at INFO after to_a2a() returns, regardless of what was configured before.

Environment Details:

• ADK Library Version (pip show google-adk): 2.11.0 (main at b3ccb29)
• Desktop OS: Linux
• Python Version (python -V): 3.11.16

Model Information:

• Are you using LiteLLM: No
• Which model is being used: N/A, not model related

🟡 Optional Information

Regression:
No. The line has been there since to_a2a was first added.

Minimal Reproduction Code:

import logging

from google.adk.a2a.utils.agent_to_a2a import to_a2a
from google.adk.agents import LlmAgent

logging.basicConfig(level=logging.INFO)
logging.getLogger("google_adk").setLevel(logging.DEBUG)

app = to_a2a(LlmAgent(name="probe", model="gemini-2.5-flash"))

print(logging.getLevelName(logging.getLogger("google_adk").level))  # INFO

How often has this issue occurred?:

• Always (100%)

Additional Context:
Happy to send a PR for this. The fix is to drop the setLevel call (the adk_logger variable is still used by two warnings further down) and add a regression test.