Found docs updates needed from ADK python release v1.14.0 to v1.14.1

I have analyzed the changes between ADK Python releases `v1.14.0` and `v1.14.1`.
Here are the recommended updates for the ADK documentation:

1. **New Spanner `similarity_search` tool**.
A new tool `similarity_search` has been added to the Spanner toolset. The documentation should be updated to include this new tool.

**Proposed Change**:
In `docs/tools/built-in-tools.md`, add a new section for the Spanner toolset, similar to the BigQuery section, and document the `similarity_search` tool.

**Reasoning**:
This is a major new feature that needs to be documented for users to be able to use it.

**Reference**:
- https://github.com/google/adk-python/commit/0c1f1fadeb5a6357af9cad0eff5d5e7103fc88b0
- `src/google/adk/tools/spanner/search_tool.py`
- `src/google/adk/tools/spanner/spanner_toolset.py`

2. **Update Gemini Model to `gemini-2.5-flash`**.
The default Gemini model has been updated from `gemini-2.0-flash` to `gemini-2.5-flash`. All occurrences of `gemini-2.0-flash` and `gemini-1.5-flash` in the documentation should be updated.

**Proposed Change**:
Replace all instances of `gemini-2.0-flash` and `gemini-1.5-flash` with `gemini-2.5-flash` in the following files:
- `docs/a2a/quickstart-consuming.md`
- `docs/a2a/quickstart-exposing.md`
- `docs/agents/config.md`
- `docs/agents/custom-agents.md`
- `docs/agents/llm-agents.md`
- `docs/agents/models.md`
- `docs/agents/multi-agents.md`
- `docs/artifacts/index.md`
- `docs/deploy/gke.md`
- `docs/get-started/quickstart.md`
- `docs/get-started/streaming/quickstart-streaming-java.md`
- `docs/get-started/streaming/quickstart-streaming.md`
- `docs/observability/arize-ax.md`
- `docs/observability/logging.md`
- `docs/observability/phoenix.md`
- `docs/observability/weave.md`
- `docs/plugins/index.md`
- `docs/safety/index.md`
- `docs/sessions/memory.md`
- `docs/sessions/state.md`
- `docs/streaming/custom-streaming-ws.md`
- `docs/streaming/custom-streaming.md`
- `docs/streaming/streaming-tools.md`
- `docs/tools/built-in-tools.md`
- `docs/tools/google-cloud-tools.md`
- `docs/tools/mcp-tools.md`
- `docs/tools/openapi-tools.md`
- `docs/tools/third-party-tools.md`
- `docs/tutorials/agent-team.md`

**Reasoning**:
To ensure the documentation is up-to-date with the latest recommended model.

**Reference**:
- https://github.com/google/adk-python/commit/0c1f1fadeb5a6357af9cad0eff5d5e7103fc88b0
- `src/google/adk/models/google_llm.py`

3. **New `save_live_audio` flag in `RunConfig`**.
A new flag `save_live_audio` has been added to `RunConfig` to save live audio data.

**Proposed Change**:
In `docs/runtime/runconfig.md`, add a new row to the parameters table for the `save_live_audio` flag.

**Reasoning**:
To document the new feature for live agents.

**Reference**:
- https://github.com/google/adk-python/commit/0c1f1fadeb5a6357af9cad0eff5d5e7103fc88b0
- `src/google/adk/agents/run_config.py`

4. **BigQuery Tool `location` parameter**.
The BigQuery toolset now supports a `location` parameter.

**Proposed Change**:
In `docs/tools/built-in-tools.md`, update the BigQuery toolset description to include the new `location` parameter.

**Reasoning**:
To document the new feature for the BigQuery toolset.

**Reference**:
- https://github.com/google/adk-python/commit/0c1f1fadeb5a6357af9cad0eff5d5e7103fc88b0
- `src/google/adk/tools/bigquery/client.py`
- `src/google/adk/tools/bigquery/config.py`
- `src/google/adk/tools/bigquery/metadata_tool.py`
- `src/google/adk/tools/bigquery/query_tool.py`

5. **New `adk_documentation` and `live_agent_api_server_example` samples**.
Two new samples, `adk_documentation` and `live_agent_api_server_example`, have been added to the `adk-python` repository.

**Proposed Change**:
In `docs/get-started/index.md`, add a note about the new samples available in the `adk-python` repository, with links to the samples.

**Reasoning**:
To make users aware of the new samples.

**Reference**:
- https://github.com/google/adk-python/commit/0c1f1fadeb5a6357af9cad0eff5d5e7103fc88b0
- `contributing/samples/adk_documentation/`
- `contributing/samples/live_agent_api_server_example/`