fix: keep connector tools available to Octo

[pmbstyle]

Summary

Fix Octo tool availability under budget pressure and add a catalog-driven path for discovering and activating tools that are outside the default active set.

Problem

Google Gmail MCP was connected and discoverable, but Octo could still report that Gmail tools were visible via discover and not directly callable. The first root cause was Octo''s active tool budget trimming connector aliases like gmail_list_messages out of the final prompt toolset.

That exposed a broader issue: tools outside the active budget were effectively invisible to Octo for that run, even if they existed in the full registry.

Changes

• prioritize connector tools during Octo tool budgeting
• add tool_catalog_search as a core Octo tool that searches the full available tool catalog beyond the active budget
• keep tool_catalog_search in the always-visible core set
• expand the active toolset in the same Octo run after catalog search results, so newly found tools become directly callable on the next step
• teach Octo via system prompt how and when to use the tool catalog flow
• add regression coverage for connector budgeting, catalog visibility, and same-run tool activation

Verification

• python -m pytest tests/test_router_tool_budget.py tests/test_octo_tool_loop.py tests/test_connector_tools.py -q