Performs a web search through the configured search mode and caches the source list.

PLANNING GATE: when `plan_session_id` is provided, this tool refuses to run until the
plan is complete (all required phases done, unverified_terms covered). If you intend to
skip planning (one-shot factual lookup), call this tool with an empty `plan_session_id`.

Returns:
  - session_id      string  pass to get_sources to retrieve full source list
  - content         string  answer from API-search summarization or online model search
  - sources_count   int
  - cached          bool    true if response was served from in-memory result cache
  - budget          object  (when plan_session_id set) actual vs estimated tool calls

When you feel confused or curious about the search response content, use the session_id returned by web_search to invoke the this tool to obtain the corresponding list of information sources.
Retrieve all cached sources for a previous web_search call.
Provide the session_id returned by web_search to get the full source list.

Returns current Selvin Search MCP server configuration and tests the configured upstream connectivity.

**Key Features:**
    - **Configuration Check:** Verifies environment variables and current settings.
    - **Connection Test:** Sends request to /web_search in api mode, /models in model_online mode, or both in parallel mode.

**Edge Cases & Best Practices:**
    - Use this tool first when debugging connection or configuration issues.
    - API keys are automatically masked for security in the response.
    - Connection test timeout is 10 seconds; network issues may cause delays.

Switches the GLM-compatible model used for search summarization, persisting the setting.

**Key Features:**
    - **Model Selection:** Change the AI model for web search and content fetching.
    - **Persistent Storage:** Model preference saved to ~/.config/selvin-search/config.json.
    - **Immediate Effect:** New model used for all subsequent operations.

**Edge Cases & Best Practices:**
    - Use get_config_info to verify available models before switching.
    - Invalid model IDs may cause API errors in subsequent requests.
    - Model changes persist across sessions until explicitly changed again.

Phase 1 of search planning: Analyze user intent. Call this FIRST to create a session.
Returns session_id for subsequent phases. Required flow:
plan_intent → plan_complexity → plan_sub_query(×N) → plan_search_term(×N) → plan_tool_mapping(×N) → plan_execution

Required phases depend on complexity: Level 1 = phases 1-3; Level 2 = phases 1-5; Level 3 = all 6.