fix(proxy): don't mix googleSearch with functionDeclarations (v1internal 400)

[eddieparc]

Don't mix googleSearch with functionDeclarations (v1internal returns 400)

Problem

cloudcode-pa (v1internal) rejects any request that combines a built-in tool (googleSearch) with functionDeclarations:

HTTP 400 INVALID_ARGUMENT
Please enable tool_config.include_server_side_tool_invocations to use Built-in tools with Function calling.

The error text suggests setting tool_config.includeServerSideToolInvocations, but that flag does not work on this endpoint — verified end-to-end (debug-dumped the exact upstream body with the flag set; v1internal still returns the same 400). So built-in tools and function calling genuinely cannot be combined here.

This breaks real coding clients (pi, opencode) routed through the proxy: their requests always carry function tools, and as soon as web search is also active (an -online model, or a client-supplied web_search tool) the upstream 400s.

Root cause

The OpenAI mapper already avoided the mix: inject_google_search_tool() skips googleSearch when functionDeclarations are present. The Gemini-native and Claude mappers did not — they injected googleSearch alongside functionDeclarations (the Claude mapper even had supports_mixed_tools for Gemini 2.0/2.5/3, and two shipped tests asserted the mix, which were failing on main).

resolve_request_config already computed contains_non_networking_tool(...) into _has_non_networking but never used it.

Fix

• common_utils::resolve_request_config — gate web-search mode on has_non_networking:

  let enable_networking = (is_online_suffix || has_networking_tool) && !has_non_networking;

  When real (non-networking) function tools are present, stay in agent mode: no googleSearch injection, no "search engine bot" system prompt, no search-model downgrade. Applies to all protocols.
• claude::build_tools — never inject googleSearch when functionDeclarations are present (matches the OpenAI mapper).

Pure web-search requests (only a web_search tool, no other functions) still enable grounding.

Verification

Unit tests (cargo test --lib):

• Repurposed the previously-failing test_mixed_tools_injection_* tests to assert the no-mix behavior.
• Added test_networking_disabled_when_function_tools_present and test_networking_enabled_for_pure_web_search.
• Targeted run: 8 passed / 0 failed. Remaining full-suite failures are pre-existing on main (thinking-budget global-state leakage, retry parsing, etc.) and unrelated.

Live, end-to-end against cloudcode-pa (release build):

• functionDeclarations + -online → HTTP 200 (was 400).
• coding tool + web_search tool together (real pi scenario) → HTTP 200.
• pure web search → HTTP 200 with grounded answer + sources.