Merge https://github.com/google/adk-python/pull/5218
### Link to Issue or Description of Change
**1. Link to an existing issue (if applicable):**
(None, this is a new sample)
**2. Or, if no issue exists, describe the change:**
**Problem:**
There was no sample demonstrating how to use `LocalEnvironment` with `EnvironmentToolset` for manual skill activation (discovering and loading skills by reading files) instead of using the pre-configured `SkillToolset`.
**Solution:**
Created a new sample `local_environment_skill` that demonstrates this pattern:
- Agent is instructed to find skills in `skills/` folder using the `find` command.
- Agent loads skills by reading `SKILL.md` using the `ReadFile` tool.
- Added a weather skill sample and reference data to demonstrate usage.
### Testing Plan
**Unit Tests:**
*(This is a sample/demonstration, so no new unit tests were added for the framework itself.)*
**Manual End-to-End (E2E) Tests:**
1. Ran `adk web contributing/samples`.
2. Interacted with the agent in the Web UI.
3. Prompt: "Can you check the weather in Sunnyvale?"
4. Verified that the agent successfully used `find` to locate the skill, read `SKILL.md`, read `weather_info.md`, and answered correctly.
### 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.
- [x] I have manually tested my changes end-to-end.
COPYBARA_INTEGRATE_REVIEW=https://github.com/google/adk-python/pull/5218 from google:samples/local_env_skill 39404309e8b9237a279ecd6ed14bb87eb84098f0
PiperOrigin-RevId: 897229752
Wei (Jack) Sun
2cbb523069