chore: add @OverRide decorators to LoggingPlugin callback methods

Merge #4572

### Link to Issue or Description of Change
**1. Link to an existing issue (if applicable):**
- Closes: #4496

**2. Or, if no issue exists, describe the change:**

**Problem:**

`LoggingPlugin` overrides 12 callback methods from `BasePlugin` but none use the `@override` decorator. Every other plugin in the package (`DebugLoggingPlugin`, `ReplayPlugin`, `RecordingsPlugin`, `EnsureRetryOptionsPlugin`, `_RequestIntercepterPlugin`) already follows this practice. With `mypy --strict` enabled in `pyproject.toml`, missing `@override` means renamed or removed base-class methods would be silently missed in `LoggingPlugin` while being caught everywhere else.

**Solution:**

Import `override` from `typing_extensions` and decorate all 12 overridden callbacks. Purely additive: one import line and 12 decorators. No behavioral, API, or runtime change.

### Testing Plan

**Unit Tests:**
- [ ] I have added or updated unit tests for my change.
- [x] All unit tests pass locally.

No new tests are required — `@override` is a static-analysis-only decorator with no runtime effect. Ran `mypy` on the file before and after the change: same preexisting warnings, no new errors introduced. CI will validate via the existing test suite and linting checks.

**Manual End-to-End (E2E) Tests:**

Not applicable. This change adds only decorators with no runtime behavior. Verified by comparing `mypy` output before and after — no new errors.

### Checklist

- [x] I have read the [CONTRIBUTING.md](https://github.com/google/adk-python/blob/main/CONTRIBUTING.md) document.
- [x] I have performed a self-review of my own code.
- [x] I have commented my code, particularly in hard-to-understand areas.
- [ ] I have added tests that prove my fix is effective or that my feature works.
- [x] New and existing unit tests pass locally with my changes.
- [ ] I have manually tested my changes end-to-end.
- [ ] Any dependent changes have been merged and published in downstream modules.

### Additional context

I am the author of the original issue (#4496). A previous PR (#4544) was opened but is pending clarification, so I'm
submitting this complete PR as the original issue author.

COPYBARA_INTEGRATE_REVIEW=#4572 from cchinchilla-dev:feat/add_override_decorators_to_loggingplugin_4496 142ed87
PiperOrigin-RevId: 875811966

Author: cchinchilla-dev

src/google/adk/plugins/logging_plugin.py

@@ -19,6 +19,7 @@
 from typing import TYPE_CHECKING
 
 from google.genai import types
+from typing_extensions import override
 
 from ..agents.base_agent import BaseAgent
 from ..agents.callback_context import CallbackContext
@@ -66,6 +67,7 @@ def __init__(self, name: str = "logging_plugin"):
     """
     super().__init__(name)
 
+  @override
   async def on_user_message_callback(
       self,
       *,
@@ -87,6 +89,7 @@ async def on_user_message_callback(
       self._log(f"   Branch: {invocation_context.branch}")
     return None
 
+  @override
   async def before_run_callback(
       self, *, invocation_context: InvocationContext
   ) -> Optional[types.Content]:
@@ -99,6 +102,7 @@ async def before_run_callback(
     )
     return None
 
+  @override
   async def on_event_callback(
       self, *, invocation_context: InvocationContext, event: Event
   ) -> Optional[Event]:
@@ -122,6 +126,7 @@ async def on_event_callback(
 
     return None
 
+  @override
   async def after_run_callback(
       self, *, invocation_context: InvocationContext
   ) -> Optional[None]:
@@ -134,6 +139,7 @@ async def after_run_callback(
     )
     return None
 
+  @override
   async def before_agent_callback(
       self, *, agent: BaseAgent, callback_context: CallbackContext
   ) -> Optional[types.Content]:
@@ -145,6 +151,7 @@ async def before_agent_callback(
       self._log(f"   Branch: {callback_context._invocation_context.branch}")
     return None
 
+  @override
   async def after_agent_callback(
       self, *, agent: BaseAgent, callback_context: CallbackContext
   ) -> Optional[types.Content]:
@@ -154,6 +161,7 @@ async def after_agent_callback(
     self._log(f"   Invocation ID: {callback_context.invocation_id}")
     return None
 
+  @override
   async def before_model_callback(
       self, *, callback_context: CallbackContext, llm_request: LlmRequest
   ) -> Optional[LlmResponse]:
@@ -179,6 +187,7 @@ async def before_model_callback(
 
     return None
 
+  @override
   async def after_model_callback(
       self, *, callback_context: CallbackContext, llm_response: LlmResponse
   ) -> Optional[LlmResponse]:
@@ -206,6 +215,7 @@ async def after_model_callback(
 
     return None
 
+  @override
   async def before_tool_callback(
       self,
       *,
@@ -221,6 +231,7 @@ async def before_tool_callback(
     self._log(f"   Arguments: {self._format_args(tool_args)}")
     return None
 
+  @override
   async def after_tool_callback(
       self,
       *,
@@ -237,6 +248,7 @@ async def after_tool_callback(
     self._log(f"   Result: {self._format_args(result)}")
     return None
 
+  @override
   async def on_model_error_callback(
       self,
       *,
@@ -251,6 +263,7 @@ async def on_model_error_callback(
 
     return None
 
+  @override
   async def on_tool_error_callback(
       self,
       *,