[codex] Add search term coverage for tool_search

[pakrym-oai]

Why

tool_search already had solid end-to-end coverage for discovery and follow-up execution, but it did not prove that distinct pieces of indexed search text actually work in integration. In particular, we were not exercising whether unique tool names, descriptions, namespaces, underscore-expanded dynamic names, and schema-property terms were sufficient to surface the expected deferred tools.

This change adds focused integration coverage for those term sources so regressions in search text construction are caught by a real TestCodex flow instead of only by lower-level unit tests.

What changed

• added a small helper in core/tests/suite/search_tool.rs to assert that a tool_search_output contains an expected namespace child tool
• added an MCP integration test that issues several tool_search_calls and verifies distinct query terms match the expected app tools:
  • exact tool name: calendar_timezone_option_99
  • tool description phrase: uploaded document
  • top-level schema property: starts_at
• added a dynamic-tool integration test that verifies distinct query terms match the expected deferred dynamic tool:
  • exact name: quasar_ping_beacon
  • underscore-expanded name: quasar ping beacon
  • description phrase: saffron metronome
  • namespace: orbit_ops
  • schema property: chrono_spec

Validation

• cargo test -p codex-core tool_search_matches_

Docs

No documentation update needed.