fix(codemode): treat tools.search as the built-in search

[rekram1-node]

Weaker models frequently write tools.search({ query }) instead of the bare search({ query }), since every other codemode callable lives under tools.. Today that fails with Unknown tool 'search'. … Use search to find available tools., which from the model's point of view is what it just did, and it tends to give up on discovery and guess.

This routes tools.search(...) to the built-in search tool when no tool is registered at the root search path. A registered root-level search tool still takes precedence, so nothing is reserved. The alias goes through the same executeTool path, so input validation, call accounting, and hooks are identical to the bare call.

Observed while evaluating subagent model selection on opencode/glm-5.3-flash: it wrote tools.search(...) in 5 of 10 runs that needed tool discovery, and every one of those derailed.

Tests: alias returns the same result as bare search; a registered root search tool wins.