fix: lazy-load CLI execution helpers

[honor2030]

Summary

• Lazy-load browser_harness.helpers only when executing browser-harness -c ...
• Keep maintenance commands such as --version and --help from importing user-editable BH_AGENT_WORKSPACE/agent_helpers.py
• Preserve -c helper availability, including agent workspace helpers, via a dedicated execution namespace

Root cause

run.py imported from .helpers import * at module import time. Since helpers.py immediately loads BH_AGENT_WORKSPACE/agent_helpers.py, even safe maintenance commands could fail or trigger user helper side effects before main() handled --version/--help.

Test Plan

• RED: uv run --with pytest --with-editable . python -m pytest tests/unit/test_run.py::test_maintenance_commands_do_not_load_agent_helpers tests/unit/test_run.py::test_execution_globals_load_agent_workspace_helpers -q failed before the fix because --version loaded the raising agent_helpers.py and _execution_globals did not exist.
• GREEN: uv run --with pytest --with-editable . python -m pytest tests/unit/test_run.py::test_maintenance_commands_do_not_load_agent_helpers tests/unit/test_run.py::test_execution_globals_load_agent_workspace_helpers -q → 2 passed
• uv run --with pytest --with-editable . python -m pytest tests/unit/test_run.py -q → 14 passed
• uv run --with pytest --with-editable . python -m pytest tests -q → 96 passed
• uv run --with-editable . python -m compileall -q src tests
• uv run --with pip --with-editable . python -m pip check → No broken requirements found.
• uv run --with pip-audit --with-editable . pip-audit → No known vulnerabilities found (local package skipped because it is not on PyPI)
• uv run --with ruff --with-editable . ruff check --select B src/browser_harness/run.py tests/unit/test_run.py → All checks passed!

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Summary by cubic

Lazy-load CLI helpers so --help and --version run without importing user workspace code. Scripts run via stdin or -c still get access to browser_harness.helpers and workspace helpers.

• Bug Fixes
  • Load helpers inside _execution_globals() only during code execution.
  • Keep maintenance commands from importing BH_AGENT_WORKSPACE/agent_helpers.py.
  • Execute code with a namespace exposing public names from browser_harness.helpers.

^{Written for commit 3f7116d. Summary will update on new commits.}

[cubic-dev-ai]

No issues found across 2 files