Allow resolve to use Julia arguments

[cjdoris]

Summary

• add a julia_args argument to juliapkg.resolve()
• pass those arguments to both Julia subprocesses used during resolution
• rename the internal run_julia() helper to run_script() and forward subprocess keyword arguments
• document the new API and add repository-local agent instructions

Motivation

Downstream packages such as JuliaCall may start Julia with cache-affecting options such as --check-bounds=yes. They can now pass those options into JuliaPkg so that parallel AOT precompilation uses compatible settings, without JuliaPkg needing to understand downstream configuration variables.

This provides the JuliaPkg side of the proposed solution for #92.

Validation

• uv run pytest -q — 125 passed, 5 skipped
• uv run pre-commit run --all-files — passed
• git diff --check — passed