fix: add support for detecting Apple Command Line Tools stubs in executors and detectors

[shubham-stepsecurity]

What does this PR do?

Type of change

• Bug fix
• Enhancement
• Documentation

Testing

• Tested on macOS (version: ___)
• Binary runs without errors: ./stepsecurity-dev-machine-guard --verbose
• JSON output is valid: ./stepsecurity-dev-machine-guard --json | python3 -m json.tool
• No secrets or credentials included
• Lint passes: make lint
• Tests pass: make test

Related Issues

[Copilot]

Pull request overview

This PR adds macOS-specific protection to avoid invoking Apple Command Line Tools (CLT) “install prompt” shims (notably under /usr/bin/) during Python-related detection/scanning, preventing disruptive GUI prompts on machines without CLT installed.

Changes:

• Extends the executor.Executor interface with IsAppleCLTStub(ctx, binPath) and implements it in Real, Mock, and UserAwareExecutor.
• Updates Python detectors/scanners to skip /usr/bin/ CLT shim binaries when CLT is not installed, and adds targeted unit tests.
• Includes minor gofmt/alignment-only edits in several files.

Reviewed changes

Copilot reviewed 9 out of 13 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/model/model.go	Formatting/alignment-only struct field changes.
internal/executor/executor.go	Adds IsAppleCLTStub to the interface and implements CLT presence probing + caching in Real.
internal/executor/user_aware.go	Forwards IsAppleCLTStub to the wrapped executor.
internal/executor/mock.go	Adds CLT-installed flag + IsAppleCLTStub behavior to the mock.
internal/executor/mock_test.go	Adds unit tests covering mock CLT-stub detection behavior.
internal/detector/pythonscan.go	Skips invoking Apple CLT shim binaries during global Python scanning.
internal/detector/pythonscan_test.go	Adds tests ensuring stub binaries are skipped without CLT and scanned with CLT.
internal/detector/pythonpm.go	Skips invoking Apple CLT shim binaries for Python PM detection and pip package listing.
internal/detector/pythonpm_test.go	Adds tests for skipping stubs on darwin without CLT + ensuring behavior on darwin with CLT and on linux.
internal/detector/brew.go	Formatting/alignment-only struct field changes.
internal/detector/aicli.go	Comment formatting adjustments.
internal/detector/aicli_test.go	Minor spacing/alignment in test table.
internal/detector/agent.go	Minor spacing/alignment in struct definition.

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