Auto-detect and prefer user-installed CLI tools over built-in

### Describe the feature or problem you'd like to solve

The agent has no mechanism to discover equivalent tools on PATH to either opt for them first or use them as a fallback. It continues with a failing or inferior tool

### Proposed solution

- Reduces friction
- Reduces wasted turns
- It uses the tools that I use so I can easily trace what happened

### Example prompts or workflows

- "Find all usages of interface across this repo"
- "Lint all the modified typescript files"
- "Search this project for todo comments and summarize them"
- "Run tests for this module/component. Iterate until they pass"
- "Find all files larger than 1 mb in this directory and sub directories

### Additional context

_No response_

The issue does not identify files, tests, or entry points for PATH discovery and tool preference. Start by locating the CLI's built-in tool definitions and command execution flow; done means equivalent user-installed tools can be discovered and preferred or used as fallbacks for the listed workflows.

Written by the indexing model from the issue text.