## Why
`tool_search` still carries the server-specific result-cap path added in
#17684 for `computer-use`: when the model omitted `limit`, a matching
result expanded the search to 20 and then `limit_results_by_bucket`
applied per-bucket caps. That makes default result handling depend on a
one-off server exception instead of the single
`TOOL_SEARCH_DEFAULT_LIMIT` path.
This PR removes that custom branch so omitted `limit` values use the
ordinary global default consistently. The implementation being retired
is the pre-change bucketed search path in
[`tool_search.rs`](5e3ee5eddf/codex-rs/core/src/tools/handlers/tool_search.rs (L121-L190)).
## What changed
- Collapse `ToolSearchHandler::search` back to one BM25 search with the
resolved limit.
- Remove `limit_results_by_bucket`, the `computer-use` constants, and
the omitted-limit plumbing that only existed for the override.
- Drop dead `ToolSearchEntry::limit_bucket` metadata from deferred MCP
and dynamic search entries.
- Remove tests and helpers that only asserted the deleted override
behavior.
- Add direct handler-level unit coverage for omitted/default and
explicit `tool_search` result limits.
## Validation
- `cargo test -p codex-core tool_search`
- The matching unit tests passed, including the new omitted/default and
explicit result-limit coverage.
- The broader `--test all` search-tool fixture phase then failed before
sending mocked response requests in
`tool_search_indexes_only_enabled_non_app_mcp_tools` and
`tool_search_uses_non_app_mcp_server_instructions_as_namespace_description`.
- `cargo test -p codex-core`
- The touched tool-search coverage passed before the run later aborted
in
`tools::handlers::multi_agents::tests::tool_handlers_cascade_close_and_resume_and_keep_explicitly_closed_subtrees_closed`
with a stack overflow.
1ae9867296